Can I use them in Roblox? My daughter loves to play with it and Roblox Studio, and having more assets to use (buildings and pre-built places she could modify) would be awesome.
Yep! We've been testing it out ourselves and Roblox does a great job at importing our models. There are a few quirks (Roblox can't perfectly handle our trees and Subway entrances), but I'm sure your daughter will have a lot of fun with them. My one piece of advice is to start small when downloading areas and slowly move your way up in size because Roblox is not always able to process larger models.
There are some limitations with getting big mesh models into Roblox but it's definitely possible - I'll ask if my engineer who's been working on testing that if he has recommendations.