Ok. So laying aside variant games (The All Decker game, the Astral exploration team, the Doc Wagon crew etc). For Generic Shadowruny Hi-jinks I argue the following as the base line. A Face. Someone gotta make the get paid roll and ensure your team isn't shut down by a grump security guard with a clip board. A Magic User, you need Counterspelling over watch, Astral issues meaning spirits and the like, a Combat specialist Street Sam/Adept/Gun Nut/tanks etc, someones gotta keep the group from getting overrun by a group of go gangers, and get shot), and lastly a Decker, gotta keep the matrix on lock.
So I vote 4 necessary roles. There are plenty of variants in there, you could basically combine an two of the roles into one character with some effort and some what lower level of effectiveness. (Mage/Face, Decker/Sam etc).
After that things are much more open to discussion, Riggers are interesting, they can be something of a wild card, just depending on how they are built, one rigger could be an amazing wheel man where another is walking army of drones, still another can be a scout with micro drones running a muck. They could potentially fill the combat role, if built correctly.
A jack of all trades can be a useful character.
A B&E specialist
A Sniper or heavy weapon specialist Possibly.
An investigator