Bird,
I'm a quad skater, not a rollerblader, but I've heard good things about the K2 skates, as far as an outdoor recreational skate. That would probably be your best bet if your ankles are not that strong. There are low cut speed boots/skates, with Bont being the most affordable/best beginner skate out there, but they don't have the ankle support, so with a weak ankle like the formerly sprained one, those aren't likely a good idea. You could go to quads, if you're comfortable with them...you at least don't have to constantly balance those to keep your ankles straight, which is why I use them, but also because I'm old and never really got the hang of inlines.
If you go to a skating rink, they would most likely have inline skates there for sale, and also for renting. You could try some on, to see which ones you like best, before you buy. K2s can sometimes be found on sale at sporting goods stores, like Gart Sports, GI Joe's, or similar outdoor sporting goods stores. Oh, Big5 is usually a good resource to check out, too, as they are always marking stuff down to clearance prices.
Have fun with the skating!
PS- on the swollen ankles, if that is what you mean by "huge", try some plain old rubbing alcohol. Standing or sitting for long periods causes poor circulation and fluid will pool in the ankles like that. Other causes are a high sodium diet, so you might start noticing the sodium content of the foods you are eating. Anyway, after work, or right before bed, pour a little rubbing alcohol onto your ankles, rub it in with both hands, and do the lower legs as well. It works some juju on it and gets that fluid out of there. You can do it in the morning, too, and that will help, but most helpful is to cut back on sodium in the diet, and try not to sit or stand still any longer than necessary..if you have a choice at work, take as many cart runs as you can, anything that keeps you moving will help. Switch out your computer chair for a nice big exercise/swiss ball once in a while...that will remind you not to slouch, and you can move on it a little, to keep your legs a little less likely to cramp up or get all swollen.
Good shoes are also a must, for work like that. They might be ugly, but that's why nurses and waitresses wear special shoes. At least go with a well padded and supportive running shoe, or any shoe you find gets you through the day without killing your feet, like you may be able to do well in berkenstocks, crocs or chacos, depending on the fit...the crocs actually kill my feet, but other folks rave on them, so I'm sure it's just about what fits, what cushions you from the hard surfaces, and supports your arch/foot in a way that's comfortable for you.