An away win in Llanelli over Scarlets saw Warriors reach their first European final while they prepare to face Munster at Scotstoun on Friday with a URC semi-final spot up for grabs.
Speaking in The Herald, Fagerson said: "The rotation is great for the players. It breeds great competition in training. Everyone is chomping at the bit, everyone wants to play, and Franco has got trust throughout the whole squad.
"It keeps everyone on their toes. And when people do get their opportunity, that's when they take it with both hands."
Fagerson also highlighted the role played in the build-up to each game by the players not selected in the matchday squad.
"Our non-23 have been huge for the last couple of months, really bringing it on a Tuesday and Thursday," Fagerson added. "And that's what you want going into knockout rugby."
Back-row man Fagerson has has also put in an unscheduled shift at centre for Warriors after Jamie Dobie, Huw Jones and Cole Forbes were forced off through injury during the game against Connacht last month. With only two backs on the bench, Fagerson lined up as an auxiliary centre for the final 25 minutes. Warriors managed to hang on for a 29-27 win but Fagerson hopes he doesn't want to make a habit of it.
"We'd sort of prepped it a little bit during the week, and we know that with a six-two split if we do get injuries in the backs then we've got people who can slot in there," said Fagerson in The Scotsman. "I think we were pretty calm when we came on: everyone knew what they were up to. Pete Horne [Glasgow's assistant coach] was coming on giving the messages. Yeah, I enjoyed it: whatever I can do for the team. It's good to know that we've got that cover.
"In my last year at school I played a lot at 12," he said. "I did a lot of the kicking as well. So I've got a little bit of experience there. Hopefully Franco doesn't start typing to pick me as a 12 usually, but I have had a couple of games there. Thankfully 12 is not too hard, When you get to 13 or on the wing you definitely have to make more decisions that are on the line. Thankfully I managed to slot in at 12. It's probably easier to defend there - I defend there off lineouts quite a bit. It wasn't too difficult and thankfully we'd prepped a little bit in the week."