You'll need to make it have high happiness/friendship during the day to make it evolve into Roselia.
mightyena doesn't evolve on Pokemon pearl, he doesn't evolve in any Pokemon game!
evolve snowver at level 40
Buizel evolve at level 26.
IT DOESN'T EVOLVE
level 18
at level 30
level 50
Level 18
Level 20.
at level 14
Level 20
Level 37