Not kept rollers before, but I've kept and raced pigeons for 15 years also kept tumblers. I'd say see what there like come spring time They'll be a bit older and plenty of time to get them out. Nice blue sky and a bit of sun they'll come good .I'm sure as a rule young rollers don't fly high . like I said dont expect youngsters to start doing the business straight away.
Good luck with them.?