Warning: Long Analysis Post Ahead
The beauty of trolls in particular is you don’t need to pick a specific tribe. You can pick one of the big ones, or dabble in some of the smaller groups and it’ll still work out. You may not like the Drakkari since they’re all more brutish warriors and priests, so here’s a run down of the rest:
Forest Trolls
Amani - you would likely follow Halazzi the Lynx as a rogue, and they were one of the strongest of the tribes. They were one of the ruling houses but were torn apart by the Troll Wars, and further hurt when the blood elves invaded their territory alongside the Alliance and crippled them further. They’re the ancestors of all forest trolls.
Firetree Tribe - technically an evil group that worked with the orcs in the Second War, but that also means you could play an assassin that used to work with the old Horde. Would be a bit harder, though.
Mossflayer - they’re a small sect that live in the Eastern Plaguelands that used the plague to their advantage when destroying human settlements. Again, as a rogue you could have been an infiltrator that sowed chaos against humanity.
Reventusk - these guys live in the Hinterlands, and they’re allied with the current Horde. They aren’t much for fighters, however, so your rogue would likely be more of a scout in this role. They’re also trickier and focus more on negotiations.
Smolderthorn - they’re another group part of the old Horde that live in Blackrock. They despise all other forest trolls and are considered insane (along with the Firetree), so they’re lovely for some more manic, crueler trolls that aren’t affiliated directly or immediately with the Horde.
Vilebranch - they’re the enemies of the Revantusk in the Hinterlands, and they’re all about sacrifices to their Loa, Shadra. As a member here, you would likely be the one looking for potential sacrifice candidates, scouting out areas to home Shadra’s clutches of eggs, and silencing dissenters.
Witherbark - they’re another group like the Vilebranch who are hostile to the Revantusk. They also worship Shadra, so it really comes down to whichever tribe you want to be across. However, these guys seem to be a lower caste, and as such have mobes like “Sadists” vs. the “Shadow Hunters” of the Vilebranch.
Jungle Trolls
Atal’ai - this tribe is strictly a faction of extremists that follow Hakkar the Soulflayer. They’re fanatics, absolutely insane, and follow the Blood God’s every words. They’re mostly dark caster, but you could be one of their protectors or even one of their risen zombified trolls.
Bloodscalp - they also worship Hakkar, but not as insane as the Atal’ai. They live in Stranglethorn and are violent and brutal. May not be as worthwhile to a rogue, but an option.
Darkspear - obviously part of the Horde, there are plenty of rogues (Rokhan I believe is considered one) so you can just be a standard rogue without too much thought put into it.
Gurubashi - like the Amani, they’re the progenitors of all jungle trolls and an ancient empire. Either you’re with the group aiding in summoning Hakkar, or you’re against them wanting to stop the consumption of the God. Either way, Gurubashi are the strongest troll tribe beneath the Zandalari. A majority of them do hate Hakkar, so keep that in mind. You’d likely follow Bethekk, the Panther, for her stealth and agility.
Hakkari - these are the few that wanted to summon Hakkar to the world and worship him. They’re very few, but if you want another fanatic faction there you go.
Shatterspear and Skullsplitter - I’m going to put both here because they’re effectively the same sects, just depends on which sounds cooler to you. But they’re once again Gurubashi exiles that live in Stranglethorn and are at war with each other.
Ice Trolls
Drakkari - as I said about, Drakkari are mostly warriors and priests, but they aren’t a bad option. You would likely follow Har’koa, the leopard goddess, though the Drakkari have consumed all of their Loa so I don’t know if any are left. You could always be an assassin attempting to get revenge for her death.
Frostmane - they’re the ones that threaten the dwarves in Dun Morogh. You could always be a rogue that seeks out intelligence on the dwarves and sneaks into Iron Forge to do so.
Winterax - all but extinct, but there’s fun in playing extinct tribes or clans. They used to threaten Alterac Valley but have since vanished, leaving little behind.
Sand Trolls
Sandfury - the only named tribe of the sand trolls, they were another progenitor like the Zandalari, Gurubashi, Amani, and Drakkari. They only live in Tanaris, in Zul’farrak, but there are plenty of them still left. Again, you could either be a living troll or one of their mummified ones, which could lead to interesting scenarios. Shadra would be your loa again here.
As far as spec, Assassination is your best bet, followed by Subtlety. Outlaw could be if you want to play an unaffiliated pirate (or be a disciple of Gral) but Assassination is my go to.
I hope that helps a little.