Rögle had 2--1 before the goal-rich third period.
The team first went up in a 4-1 lead before Frölunda scored two straight goals through Nicklas Lasu and Ryan Lasch.
But when the feeling was that Frölunda was on his way to catch up, Ted Brithéns scored his third goal of the evening and thus completed his hat trick.
Ted Brithen was also the player who scored Rögle's first goal in the CHL meeting when he put 1-1 after a delicious assist by Oskar Stål Lyrenäs.
- It is an incredible delicacy.
Also nice for Brithén who has not produced so much offensively, says SVT Sports expert Maria Rooth.
- It's a great game by Oskar, it's just to thank and receive.
It was a long time ago I scored a goal so it was nice to get it over with, says the goal scorer Brithén.
Rögle won the match 5–3.
The return will be played next week and the final will be played on March 1.
The second semifinal between Munich and Tappara was also to be played tonight but had to be postponed.
Before the match, it was clear that Simon Edvinsson in Frölunda tested positive for covid-19.
The JVM player, who trained with the team as late as Monday, has been isolated after the positive test result on Tuesday morning.