be on a roll

To be experiencing a particularly successful period, especially one that has not had any setbacks, low points, or interruptions of failure. Three championship titles in a row? Wow, that team is really on a roll. Jim was really on a roll last night with his jokes—we couldn't stop laughing! It takes me a while to get some ideas down, but once I'm on a roll, I usually end up writing five or six pages a night.

be on a ˈroll

(informal) be experiencing a period of success at what you are doing: Don’t stop me now — I’m on a roll!