It's hard to answer this kind of question, which is why you've yet to receive any responses. It's really all just personal preference. Each class has their ups and downs, but they'll all fall into a role at some point. Personally, I've played every class - Holy Pally and an Enh Shaman in Vanilla. I've learned to love Mage. Casting DPS has just become a preference after considering and trying the others. I liked to heal because I liked to have that responsibility and it was challenging. Tanking was fun because the fights were in my control and that was also more challenging than DPSing, in my opinion. However, after doing that for a while, I decided to give casting DPS a try and turned out to love it more than anything else I'd done. I had fun doing every role, but I just found casting DPS to be the most fun for me. That's what it's all about in the end. All classes and specs will be played. There may be a shortage of tanks or healers, but that shouldn't be the incentive to play them. It's all about what you have the most fun with at the end of the day.
To your case specifically, rogue seems like your choice. All I needed to read to know that is, "reliving the endless fun of playing a rogue." Why not begin with that? Maybe at some point you'll want to try a caster and start leveling one as an alt. Maybe you'll find that to be more fun. There is no way of knowing until you have played them yourself and made that decision. But, based on what I am reading, rogue should be your choice. For PvP/PvE, I'm doing PvP because that's what I played on in Vanilla. If you don't do much PvPing, DO NOT play on the PvP server. In Vanilla people do a ton of PvPing because of the honor system and the incentives that come from it, there is no resilience and the gear you gain in PvE makes you equally as strong in PvP, and it's just more fun without all the garbage Blizzard kept implementing. That is just my opinion, however. Like I said, it's all about what you are feeling the most strongly about. Groups will need DPS, whether it's melee or casting. You will find groups as a rogue - that shouldn't be a concern. Healing vs DPS is just another preference thing that you have to figure out yourself. No one can tell you what you will like the most. But, like I said, from what I am reading a rogue on a PvE server is your best bet.
tl;dr - Rogue on a PvE server. You'll find groups as a rogue because every group needs DPS, whether it be melee or casting. Rogues are also good at soloing, so the group aspect shouldn't be a concern. Healing vs DPS is a preference that no one but you can decide. However, based on what I'm reading, you want to play a rogue, not heal. Ultimately, do whatever you feel that you will have the most fun with.