Rovers claimed a top-10 finish last term after a successful campaign at Ewood Park.
Roberts believes there is room for improvement and he can see no reason why they should be challenging for a spot in Europe next term if they can sort out their away form.
"It was a very good season at home but that has of course been tempered by the fact we have been terrible away from home," Roberts told the Lancashire Evening Telegraph.
"Things could have been so much different.
"It is an improvement on the season before but, to be honest, it is nothing less than we have expected.
"We wanted to be in the top 10 and want to be challenging for the Europa League and the top eight.
"We won't be doing cartwheels, we know we should be doing better.
"We know we could have done better and that is the way you need to think about things going into next season.
"We want to always do better.
"The whole time I have been here we have been looking to improve and, yes, we have improved on last season.
"But we know if we had got better results away from home things could have been better."