Because LK roll is the safest/leaves you with the most time to buffer/do that whatever.
There are three standard ways of pulling off a 360:
- Perform a normal attack. This is usually the preferred way of doing the move. Street fighter allows you to 'buffer' an attack up while doing another motion, and this is very similar to how to buffer up a charge attack as well.
Have you ever seen Zangiefs going forward and backwards, which translates to left and right, very fast before a pile diver? They do this as footsies plus they buffer 2 of the 4 required cardinal directions, they only need to input down and up + punch to execute the move.
Links are performed by executing a follow up move as soon as the first one finishes. They cannot be performed by cancelling or buffering, so they are very timing dependent and mashing is unlikely to succeed.
I think I get the gist, but I'd like a dictionary-tier definition.