Big Mom is going to be disappointed when she'll find that there no more Scabbard or Mink to smash when she'll arrive on the roof. Though she may just want to wait Luffy here, she must know that Luffy wants to go for Kaido directly and thus is heading for the roof too.
Can big mom just get to the roof though?
Think about it, she entered the tower when she didn't have to. She could've just flown up directly to the roof.
I don't think Zues and Prometheus are conscious and can take her to the roof.
Meaning big mom is going to take the stares. Meaning it's gonna take WAYYY long for her to reach the roof if she even makes it there
Remember udon where Big mom took days to reach udon just because oda wanted to waste time. Since big mom needs to take the stares, oda will waste as much time as he wants with her again