Hmm... Well, my own opinon on this matter... In each series, you have the Goggleboy, the Lone Wolf, the Keeper, and actually a Late Joining type person.
In the Adventure, that would be Hikari, in 02, Ken, in Tamers that-guy-with-the-Cyberdramon-whom's-name-I-can-never-remember, in Frontier you had Kouji's brother, and in Savers you had Ikuto. So, going on what I was seeing earlier, there's at least 4 major roles in digimon, and often most anime for that matter.
But, well, I guess I agree with what was said earlier about 02, that it didn't do as good of a job with them. It DID have all the roles, though. Daisuke as the Goggleboy, Iori was the Lone Wolf (but to a much less degree from what I saw), Miyako was the Keeper (again, to a lesser extent), and Ken was the Late Joiner.
But... well, personally, here's what I see:
The Goggleboy is the leader, and often has a Fire/Dinosaur based digimon.
The Lone Wolf is there as support, and usually has a wolf or beast-type digimon. How fitting.
The Keeper keeps everyone together in hard times. Their digimon didn't have a set type, though.
The Late Joiner, in most cases seems to be someone who has changed sides to join the main group's side. In the case of Adventure, it was Tailmon who switched, rather than Hikari, but later, in 02 it was Ken, in Frontier it was Kouji's brother, and in Savers it was Ikuto. I missed the part in Tamers where it happened, and I could be wrong on who it is. For all I know, this role could belong to Impmon. Like with the keeper, there seems to be no general theme to what the digimon parter is, though.
But those are the 4 main roles I see being pretty much always there. So, pretty much:
The goggleboy will be a leader type with a dinosaur-like digimon.
The lone wolf will be a loner who lends their support with a beast-type digimon.
The keeper is the mediator of the group, who keeps them together.
The late joiner is the one who changes sides and joins the group as the series progresses.