The 22-year-old Bulgarian needed 55 minutes to take the first set from Rosol who broke Dimitrov's service in the third game.
Dimitrov got into his stride to take the second set in 25 minutes and finished the tournament without dropping a set.
Ranked 16th, Dimitrov reached the quarterfinals of the Australian Open where he lost to Rafael Nadal.
It was the second title of the season for Dimitrov, who won Acapulco two months ago.
“It feels good to have won,” Dimitrov told ATPWorldTour.com. “I lifted my game, not having been having with my previous matches in the tournament. I knew I had to lift my level, especially after the first set. Lukas is a very good winner, who hit some outstanding winners. It was a pleasure to play in front of Ilie Nastase and other greats.
“I have worked really hard to start winning titles. I have put in enough effort, time and sacrifices to get here.”