Some roles, like defender, may not work as well without using a combat grid / miniatures - that's a real thing to think about as that becomes optional.
Personally, I'd like to drop two of the roles with prejudice - Controller and Leader.
Controllers by general design focus are intended to _make combats more boring_. Freezing half the enemies in place so they can't act, stunning the big boss for an entire combat, sleeping this or that, etc. In play, some of them (thankfully) fail at that, or only do so in some of the combats and not others - though that tends to mean the most dangerous and exciting combats are the ones trivialized by a barrage of spells (swinging back towards 15 minute day problems). The more I play, the happier I am to say that everyone can get a little control (daze, slow, forced movement, whatever) without making it the entire focus of a character.
Leaders... well, technically I'm fine with having healers. But I'd like to drop the _Leader_ part. I don't need people granting everyone a ton of attacks, or fiddly bonuses to track constantly. Don't center a character on making everyone else's turns more complicated and giving people things to track and forget.
So, yeah, my roles might look something like:
Defender: Tougher, slightly better defenses, in an optimal world reduces total party damage taken
Healer: Increases party's ability to recover from damage taken
Hopefully in vaguely similar terms - so if a group can effectively take 10 hits before dropping, swapping in a defender or healer might up that to 12.
Striker: Focuses on killing one target more quickly
Blaster: Focuses on killing multiple targets
Both of which would effectively shorten combat rounds. So if a group was taking 12 attacks over 5 rounds without, swapping a striker or blaster in might kill things faster so they only take 10 attacks.
Note that _functionally_ all 4 of those roles resulted in the same thing, better party survivability through shifting about 20% of incoming damage. I'm a big fan of personal choice - not having a particular role should be fine, and having extra should be fine.