Hard to say there's a "prospect pool" since everyone ends up playing for the team. If you want to break it down by age/experience:
23 and under (and less than 3 years of NBA experience)
1) Terrence Ross, SF (23, 2 yrs experience) - good shooter, excellent athlete, could take the next step to being a good defender and becoming a very nice role player. Or he could really step up his offence and be like DeRozan 2.0, but with a better shot.
2) Jonas Valanciunas, C (22, 2 yrs NBA experience) - Potential to be an excellent NBA Centre in a time where there are precious few of those. Legit size for the position, good array of offensive skills, good rebounder. Already a double-double threat most nights. Will only get better.
3) DeAndre Daniels, SF/PF (22, rookie) - Not likely to play this season (Raptors are expected to have him sign in Europe so they can "stash" him and not have to worry about him taking up a roster spot). If/when he plays he's supposed to have a decent, crafty offensive game with some range, though he realistically lacks a position.
4) Lucas Noiguera, C (21, rookie) - Acquired via trade, and not yet signed to come over from Europe. He's a tall, rail-thin C with excellent mobility and shot-blockers' instincts. Could evolve into a nice devensive presence behind Valanciunas and part of a very mobile 2nd unit.
5) Bruno Caboclo, SF (18, rookie) - tall, rail-thin SF with a huge wingspan. Already has a decent shot and looked good in Summer League, albeit with expected rough spots. He looks a lot better than people were cracking jokes about at the draft (2 years away from being 2 years away) and he has the potential to be an excellent all-around SF, though those "Brazilian Kevin Durant" comparisons are probably unfair in terms of expected production.
And then from 24-27 we have:
DeRozan (24) - Good primary scoring SG, though he could stand to shoot better. He's at least taken steps to pass the ball more and play some D.
Fields (26) - Meh depth guy making way too much money.
Amir (27) - Good energy PF who runs the floor, rebounds, and shoots better than you'd expect for a player of his skill type. Still can foul too much, his intense play style tends to get him banged up, and he's not a great defender. But he's still really useful
James Johnson (27) - Long, lanky SF with excellent defensive capability and toughness. Used to have problems going off-script and trying to be an offensive hero. Apparently he's matured and is over that. If he is, then he becomes the anchor of our defence on the wings.
Patrick Patterson (25) - Reasonably sized PF who doesn't have Amir's toughness, but is similarly athletic and a more rounded offensive player. Capable of going off every once and a while and being a surprising contributor.
Greivis Vasquez (27) - Backup PG and sometimes SG with Casey's rotational tendencies. Kind of a poor man's Jose Calderon (excellent playmaking PG who can also shoot the 3 and keep defenses honest). Not a great defender, but that's tolerable with the versatility he provides as a backup to Lowry or a running mate.
Louis Williams (27) - freshly acquired in a trade with Atlanta, he's a tiny, undersized SG who often gets miscast as a PG. Good shooter, had blazing speed before a significant knee injury, so it remains to be seen how well he bounces back to full health. Won't distribute, and can't defend actual SGs because of his size. But his niche is to be a scorer of the bench and he can do that.
At 28 and over are:
Tyler Hansbrough (28) - Grit/hustle PF who comes off the bench and gets in peoples' faces. Fills a niche.
Kyle Lowry (28) - Bulldog all-around PG who can distribute, shoot, penetrate and score, and play D (especially take charges). Provided he doesn't slack off on his fancy new contract, he's exactly the kind of leader the team needs.
Chuck Hayes (31) - Roster-filler undersized PF. I doubt we see much of him in the lineup or off the bench.
And that's how the roster breaks down.