There is no rolling versus defenseless transports. By definition, transports that can retreat are not defenseless, so combat would be conducted normally.
I know you need a destroyer in order for planes to attack them but you don’t need a destroyer for lets say your battleship to attack an enemy sub do you?
Nevermind - the answer is on pg. 16. Looks like attacking air units can either be chosen to defend against the scramble (i.e. participate in the sea battle), or can ignore the scramble and assist in the amphib assault - but cannot do both.
