There are some questions you need to ask yourself....
What size and weight item do I expect to slice most often?
The reason for this is to determine how big a "bite" you need a slicer to have, and how much weight you expect to toss at it. It's kind of over-kill to buy a huge deli slicer to help you slice dry salami, unless of course, you're cutting literally POUNDS of it. However, you can't expect a kitchen counter top model slicer to happily slice a 10 pound finished weight roast.
Since you're talking about roasting your own meat, for the most part you're talking about a 6 inch wide product to slice. Ok. Weight? Probably not more than 5 pounds. That will take you out of the range of most counter top models. There are a few that are heavier-duty...but they go for a good price too.
Compare, compare, compare. I ended up buying a retired model off eBay that has solid gearing, can handle a 10# deli roast or a 5# left over ham. We use it for buying in bulk. It's cheaper, I can control the size of the slices and the uniformity of the cut, we use it for slicing jerky and we'll be giving it a go for a few other things as we get the hang of it. It's heavy...but I can lift it, and so far, it's worth it. 1 catering gig and it'll pay for itself.