With Rosegarden and the piano roll, I can easily stretch/move each of
the MIDI notes, but I didn't find an easy way to synchronize with my
audio wave (though I haven't used Rosegarden a lot, so perhaps I missed
something).

Ideally I would like to:

+ load in one program both the audio and the MIDI file
+ see the soundwave forms for both audio and MIDI plus the piano roll
  for the MIDI file
+ if something is not synchronized properly (due to the nature of the
  music, I can see it nicely by inspectint the soundwave), I would like
  to stretch/move the MIDI notes in the piano roll and interactively see
  how the soundwave changes, so that I can immediately see if the MIDI
  and the audio are better synchronized.

Is there a tool where I can do that easily? Perhaps there is some other
procedure/tool that can help me with this?