To me, there's 3 main roles in PSO; Damage dealers, crowd control, and support. Making a distinction between melee or ranged DPS is pointless imo, and tanking is pointless period in... Just about any PSO game, correct me if I'm wrong. (And please for the love of Sato don't use Guard Stance as a positive example of tanking >.<)
However, I think specific roles are almost never assigned to people. People just adapt to the situation at hand and do what comes naturally. It just goes unspoken. The only time it really ever is brought up is to find out whose buffs/debuffs are the highest level, to decide who should take on support duty. Or maybe if I'm in an android party, we could really use some Resta spam from the one lone HUmar we have during Falz.
To piggyback on what
@Matt said, everyone is DPS, but you might also wind up CC-ing or supporting depending on what class you are and what your party composition is. So to a RAcaseal main like
@Bliz or me, support is kind of a non-option to us. We have some niche support options like healing with Star Atomizers or debuffing with Zalure Needle, but you will rarely see these things in action. Instead, we have a plethora of options for CC; Frozen Shooter for freezing high priority targets at range, Snow Queen for freezing lined up enemies, Spread Needle for groups, not to mention Freeze/Confuse Traps. But at the end of the day, we're still DPS, cuz dem mobs gon needsta die sometime, sho'nuff.
This is pretty much the same in PSO2, I might add, except crowd control might as well not exist. Status effects are nowhere near as reliable or as strong as in PSO1, so the only thing you really have for CC is hitstun, and vacuum effects like Zondeel or certain PAs. DPS is pretty much all that matters, besides the mandatory Ranger for Weak Bullet and optionally a Techer for Shifta/Deband buffs that are worth a damn.