You can do no wrong with Mastermind builds so long as you take all three summons and two upgrades from your Primary. I also prefer to take the L18 henchman support power.
For Forcefields, you should be looking to take Force Bolt, Insulation Shield, Deflection Shield, Dispersion Bubble and Force Bubble as a minimum.
Mix and match with the other primaries, secondaries and pools to taste. For flavour, here's my own Robotics/FF Build so far...
01 : Force Bolt
01 : Battle Drones
02 : Pulse Rifle Burst
04 : Insulation Shield
06 : Equip Robot
08 : Hover
10 : Deflection Shield
12 : Protector Bots
14 : Fly
16 : Assault
18 : Repair
20 : Dispersion Bubble
22 : Tactics
24 : Group Fly
26 : Assault Bot
28 : Personal Forcefield
30 : Repulsion Field
Wow, thank you... I'll use that, but change the travel power to Teleport, and of course... I'll take Insulation where you took Deflection.
Thank you so much.
Sorry for the double post:
Any chance you can post slotting suggestions?
Any secondary power for defense = 3x Def
Any secondary power toggle = 1 or 2x EndRdx
Assault = 1x EndRdx
Tactics = 1x EndRdx, 3x ToHit
Drones = 3x Acc, 3x Dam
Protector = 1x Acc, 3x Dam, 1x Heal, 1x EndRdx
Assault = 1x Acc, 4x Dam
Rifle Blast = 1x Acc, 1x Dam
Force Bolt = 2x Acc
If you're going for Teleport, drop Group Teleport (it's not really any good) and slot for 2x EndRdx on your self Teleport.
Accuracy is handled for a large part by Tactics, so no need to slot heavily on the Protector Bots and Assault Bot. Drones tend to get a lil happy about wandering out of Tactics range once in a while so benefit with the heavy slotting.
You should have plenty of slots still to move about for flavour 
Feel free to disregard everything I say!
Thank you... *bows*
I'm now level 6... got my first upgrade, and now Enchufu (my first drone), is now accompained by Trueno.
P.S. Enchufu means Plug in Spanish, respectively, Trueno means Thunder... according to Google Translators
P.S.S. Don't worry, I was gonna drop Group Teleport anyways...
Again, double post... sorry! I really am...
What are the levels at which I can summon 3 battle brones and 2 protector drones respectively?
Hmm, well I recommend reading the Guide to Modern Masterminds - which covers that sort of question Link is in my sig.
Errmm... yes, that might...
Hehe, you're on the Most Wanted List right? I saw your pic around... with a Drone! ^^
I am indeed - I have more than just a drone or two now though Full compliment here!
Zap's posted his build and I like the look of it but I thought I wopuld post mine for a bit of comparisson. I dont have any attacks so rely on my bots for damage but with all the support powers I have I can currently solo missions on the second highest difficulty without losing any bots unless faced with a very nasty boss which is what detention field is therefor at 35. Currently lvl 34 and it is very fun. Heres the build please ignore what lvl I took some of the slots at as I am not 100% sure what I slotted when adn this is a respec build anyway.
Name: Dr E Genius
Level: 41
Archetype: Mastermind
Primary: Robotics
Secondary: Force Field
---------------------------------------------
01) --> Battle Drones==> Acc(1) Acc(3) Dmg(3) Dmg(5) Dmg(5) KB_Dist(7)
01) --> Force Bolt==> Acc(1) EndRdx(7) Acc(39)
02) --> Deflection Shield==> DefBuf(2) DefBuf(11)
04) --> Insulation Shield==> DefBuf(4) DefBuf(11)
06) --> Equip Robot==> Rechg(6) Rechg(9) EndRdx(9)
08) --> Recall Friend==> EndRdx(8)
10) --> Assault==> EndRdx(10)
12) --> Protector Bots==> Acc(12) Dmg(13) DefBuf(13) Heal(15) Heal(21) TH_DeBuf(21)
14) --> Teleport==> EndRdx(14) EndRdx(15) EndRdx(31) Range(31) Range(39) Range(40)
16) --> Tactics==> TH_Buf(16) TH_Buf(17) TH_Buf(17) EndRdx(23)
18) --> Repair==> Rechg(18) Rechg(19) Rechg(19)
20) --> Dispersion Bubble==> EndRdx(20) EndRdx(34) DefBuf(37) DefBuf(40) DefBuf(40)
22) --> Personal Force Field==> DefBuf(22) DefBuf(23)
24) --> Aid Other==> Heal(24) IntRdx(25) Rechg(25) Rechg(37)
26) --> Assault Bot==> Acc(26) Acc(27) Dmg(27) Dmg(29) Dmg(34) DisDur(34)
28) --> Aid Self==> Heal(28) IntRdx(29) Rechg(31) Rechg(37)
30) --> Resuscitate==> Rechg(30) Rechg(33) Rechg(36)
32) --> Upgrade Robot==> Rechg(32) Rechg(33) Rechg(33)
35) --> Detention Field==> Acc(35) Rechg(36) Acc(36)
38) --> Force Bubble==> EndRdx(38) EndRdx(39)
---------------------------------------------
01) --> Sprint==> Empty(1)
01) --> Brawl==> Empty(1)
01) --> Supremacy==> Empty(1)
Hi folks,
Thought I would post my build too, for some comparisons with the others (as you can already see, your playstyle and preferences has a big effect on powers).
This one is tried and tested up to 40 and it rocks Although in all honesty you really have to try very hard to muck up a Robots // FF
Ignore the order I took slots...can't remember, but the powers and number of slots is about correct 
---------------------------------------------
Exported from Ver: 1.7.5.0 of the CoH_CoV Character Builder
---------------------------------------------
Name: Kalg
Level: 41
Archetype: Mastermind
Primary: Robotics
Secondary: Force Field
---------------------------------------------
01) --> Battle Drones==> Acc(1)Acc(3)Acc(3)Dmg(5)Dmg(5)Dmg(11)
01) --> Force Bolt==> Acc(1)Acc(11)Rechg(37)
02) --> Deflection Shield==> EndRdx(2)DefBuf(7)DefBuf(9)DefBuf(29)
04) --> Insulation Shield==> EndRdx(4)DefBuf(7)DefBuf(9)DefBuf(29)
06) --> Equip Robot==> Rechg(6)Empty(23)
08) --> Recall Friend==> Rechg(8)
10) --> Aid Other==> Heal(10)Heal(17)Heal(19)Rechg(19)IntRdx(39)
12) --> Protector Bots==> Acc(12)Acc(13)Dmg(13)Dmg(15)DefBuf(15)DefBuf(17)
14) --> Teleport==> EndRdx(14)EndRdx(37)Range(40)Range(40)Range(40)
16) --> Swift==> Run(16)
18) --> Health==> Heal(18)
20) --> Stamina==> EndMod(20)EndMod(21)EndMod(21)
22) --> Dispersion Bubble==> EndRdx(22)EndRdx(23)DefBuf(25)DefBuf(34)DefBuf(34)
24) --> Repair==> Rechg(24)Rechg(25)Rechg(33)
26) --> Assault Bot==> Acc(26)Acc(27)Dmg(27)Dmg(31)Dmg(34)
28) --> Assault==> EndRdx(28)EndRdx(31)
30) --> Personal Force Field==> EndRdx(30)DefBuf(31)DefBuf(39)
32) --> Upgrade Robot==> Rechg(32)Rechg(33)Rechg(33)
35) --> Tactics==> EndRdx(35)EndRdx(36)TH_Buf(36)TH_Buf(36)TH_Buf(37)
38) --> Force Bubble==> EndRdx(38)EndRdx(39)
---------------------------------------------
01) --> Sprint==> Empty(1)
01) --> Brawl==> Empty(1)
01) --> Supremacy==> Empty(1)
02) --> Rest==> Empty(2)
[b]---------------------------------------------
(I notice it says lvl 41...that might mean I have 3 more slots which I don't really have..anyway you have plenty spare, it's easy to see where you could lose 3 slots from the above without really altering effectiveness)
Ok now for the reasoning:
1) I use bots as damage dealers, don't want to get my hands dirty And bots are the most damaging mastermind set post 32 in my opinion, ninjas are good, but nothing beats the sheer AOE goodness.
2) I went without stamina for 38 levels, but I did a respec and took it, as with 4 toggles running AND trying to bubble my teammates or bots, my endurance was horrible. It also takes some of the pain out of initial summoning, plus you can resummon mid fight if things go 'breasts up'. Later on you really do NOT want to have to turn force bubble off mid fight to resummon, with several orange+ Daemons and Daemon lords itching to get in amongst your bots with smashing/dark attacks and auras...*shudders*.
3) I love Aid other and repair, definately take both, really helps survivability. I also recommend Teleport due to the Assault bot getting stuck a lot after going up lifts.
Finally a general tip!
When you enter a mission, go forward a bit and turn 90degrees sideways, so you can summon and buff all your pets. It's only when you've summoned 6 pets, applied 6 buffs, 2 of the higher buffs, turned on 4 toggles, and bubbled the main henchies then you go to click a mob to attack and realise you have clicked on the door by accident; that you truly know the meaning of pain......
Regards,
- Kal
Hey, ok... I made a Tech Rob/FF today and got him to level 5. His name is Professor Einstein, I'm proud I got that name, lol... he is infact, following a concept. He has been resurrected using robotic hearts and veins, he is essentially a robot, with human skin, but his own brain, 'except with the length of time he's been dead, he looks like a zombie.
As Tech, I decided to incorperate his genius into his invention of the Battle Drones, and the techonology of Forcefields. I've also had the idea for Teleportation (his preferred travel power)... I am planning on getting Stamina, and am not ruling out Hasten, but would prefer a build without it. (For slotting and power purposes)
At the moment... he is level 5. With the following powers/slots already chosen. All the slots are, as yet... empty, the brackets indicate the levels which I assigned the slots.
Lvl 1: Battle Drones: 3 slots (D, 3, 5)
Force Bolt: 1 slot (D)
Lvl 2: Pulse Rifle Burst: 2 slots (D, 3)
Lvl 4: Deflection Shield: 2 slots (D, 5)
If anyone could help me to finish, or plan to finish this build... I'll be very happy and grateful.
P.S. I am not planning to PvP at all in my career as a Villain, pure PvE. Boss-killing will be nice, but not essential. As a bubbler, I will be grouping alot.