roll 有“滚动”的意思，on a roll不要把它理解为“在一个卷上”。这个短语被用来比喻连续交好运或连续成功或获胜。

【例句】
I made a name for myself and I was on a roll, I couldn't see anything going wrong.
我靠自己的能力成名了，接二连三地获得成功，我觉得一切似乎一帆风顺。

I am going to bet on the hockey tonight. Our team has been on a roll this season.
今晚我要赌曲棍球。我们队本赛季接连获胜。