after rotoscoping video has black square background

hi guys

i did a rotoscope on a charachter in a video, then i export it s avi file.   then i tried to put that video on another video in premiere  it shows the charachter with black square background.

i did rotoscope already  and when im rendering it on after effects it shows that it has that white and grey background.  (means no background) but once i use this rotoscoped video it plays with square black background

any suggestions?