Big drumrolls are the same as small drumrolls and you play them the same way. If you're not worried about maximizing your score at your level you can safely ignore them as not hitting any of the drumroll ticks doesn't drop your combo.
If you haven't already, practice alternating between each hit so you're more stable in rhythm. This way, you'll be more likely to hit all the ticks without much issue. If you're worried about what fingers to use, just use what's most comfortable to you.