If you have roles that compliment each other, probably 3-4.
Infiltrator and gunbunny go hand-in-hand anyways. Since you are probably already using Cyber and have decent REA, you can add a level one Rigger Headware and be a pretty good driver.
Get tailored Pheromones 3 + a suit and you can also be a good face with a monetary investment that is doable during gameplay.
Rigger is absolutely not a complementary role, since it requires a fuckton of skills and nuyen. Same goes for Decker.
You can slap combat-capabilities onto a decker/rigger with an Arm of god, but the other way round is difficult, due to drones and Decks costing a fuckton of nuyen. IF you are able to scrounge a Deck for free during gameplay, you could make do with Skillwires and such, but thats about it.
Also keep in mind that there is a big difference in whether you want to be able to do 2-3 (or more) things at chargen or later during gameplay.
Doing more than two things during chargen works, but its usually a big tradeoff where you are cutting yourself short in many areas. Better go for two roles during chargen and lay the foundations for a third. Eg take what you need to be good at shooting and sneaking during chargen, then grab the Control Rig during gameplay.
At the moment i'm one of the teams designated combat guys, but also handle:
-explosives (11 Dice)
-mundane healing (17 Dice)
-driving (13 Dice)
-negotiating with Johnsons (10 Dice, yeah, thats sad, but the rest sucks even more in this area so i basically always spend a point on edge on this).
as secondary/tertiary fields.
We have a designated Infiltrator, so no investment in this area needed, but in theory, i COULD also go there because its fucking easy with 8 Agility.
I could also increase the negotiations capabilities a lot more, but i don't have enough essence left for both Pheromones 3 AND a pain-editor and going lower than level 3 is not worth it.
Mind you, I'm about 45 Karma in, but as you see, branching out is doable.