Hm. Roast I don't do much because we ate it on the weekly growing up (it used to be a cheap cut of meat people didn't really want..) but I do it occasionally.
Crock pot, slow cooking is best if you don't want an oven on forever. The roast is hopefully fatty enough to melt it down and be its own basting... but I do add liquid because it just freaks me out trying to cook things in a crockpot without liquids. The liquids help cook evenly, and on top of that make clean up way easier. I add beer generally, and a bottle of it is more than enough and you can probably get away with half a bottle.
(I'm the queen of freezing-for-later, and wine and beer happen to be things people tend to not polish off at parties. I don't drink beer, so I freeze wine and beer leftover in muffin tins and then store them in baggies for recipes. The beer doesn't have to be stellar quality to cook well, and in fact makes you feel less guilty about alcohol waste if you use rejected watery beer. I save fancy beers for stews.)
The vegetables themselves lend to flavor, and the roast actually has its own flavor.. the more spices you add, the more you'll alter it. I like dry rub/BBQ style spices because I'm from Texas and we put that shit on everything. But beer mellows them out, and lets the roast shine through. An alternative that you could use that's getting really popular lately is hard apple cider. Either way, something not too overpowering works. Chicken broth would definitely work and be cheaper, but I think the beer adds something to it the chicken broth just lacks.