How thick do you roll out your fondant for covering cakes?
Between 3/16"- 1/4" for us.
Mine is rolled out like pie dough.
I roll mine about 1/8" thick for round cakes and a little thicker - 3/16" for topsy turvy and square cakes which are a little harder to cover. I do use white chocolate fondant which I find is stronger and less apt to tear than other types. When I first started with fondant I used 1/4" thick but I found that the weight of the thicker fondant would cause some slumping in the buttercream (I use SMBC) but I know others haven't had this experience perhaps b/c different buttercream? - I don't know.
I did read on here that if you use a thicker, ie. 1/4" thick layer of fondant you should just use a crumb coat, ie. thin layer of bc underneath. If you use a thinner layer of fondant you can have a thicker layer of bc - this has generally held true for me.
I use choco-pan, which is designed to be able to roll really thin. One of the reasons I avoided fondant is because I didnt' like the thick "play-doh" look that I saw on many cakes. I think a thinner layer is much prettier, so I roll mine really thin. It's probably less than 1/8" thick.