From Longman Dictionary of Contemporary Englishbe on a rollbe on a rollinformalSUCCESSFUL to be having a lot of success with what you are trying to do Midvale High was on a roll, having won their last six basketball games. → roll
Examples from the Corpus
be on a roll• The Toronto-born architect is on a roll.• Two, which hold wooden blocks, are on rolling coasters, and they are permanently available.• Small business is on a roll.• Curve are on a roll now.• The master and I were on a roll now, and it seemed that nothing could stop us anymore.• Lee kept on the attack despite this and the fact that Nicklaus was on a roll.• The emergent thing is on a roll.• Baseball owners, once thought to be shackled by tradition, are on a roll. 