I've always been a big fan of herb/alch for rogues; however, that was pre BC and pre Alch nerf. Currently blizzard is changing the way elixirs stack for end game raiding and thus giving alchemy limited use. It will still be useful, don't get me wrong - but since you'll only be able to use one offensive and one defensive elixir at a time, there will be much less variety in which potions you actually create. Actually for rogues, the choice on the high end will be flasks of relentless assault (a discovered recipe) which will count as the offensive elixir. For more trivial encounters, you'll be seeing rogues using either elixirs of major agi or elixirs of fel strength.
Part of having alchemy, even in a bigger guild, is just to make your life easier (especially for raiders). The profession itself is not that profitable after you figure in raw material costs, vile costs, AH cuts, and costs for unsold potions. Before BC hit, the profession could be used to turn a reasonable profit. With the avent of the discovery system, and the new "specs" that alchs can choose, some things have changed. The market is flooded with pots of all sorts from people trying to get a discovery. There are people turning out potions by the thousand every week - driving prices down through supply and demand. In addition to this, many alchemists advertise free combines because it 1) gives them a chance to proc their spec and 2) it gives them more of a chance to discover flasks.
The alchemy market on some (probably most - maybe all) servers is screwed up right now. If you're an herb there's a good chance you will make 50-100% more profit by selling your raw herbs than making finished pots and putting them on the AH. The patch and changes are logically predicted to change this "FTL."
In either case, if you want a profession that's easy to level but provides little to no utility or profits besides being able to actively make your own consumeables (as opposed to getting a guildy/friend to do it for you)... go with alchemy. If you want a profession that actually provides something BoP and cool... go for anything else (save engineering which is currently even worse than alchemy).
JC is a cool profession. It's expensive to level up, but if you go mining/JC you'll be in good shape. Just don't push it too hard - or you'll be poor. Also, it would be a smart idea to check the AH frequently with your main and look for good deals on JC recipies. You can probably save your money in the long run if you "shop around" and snag stuff for good prices.