The Perth side secured a famous 1-0 win over the 22-time Norwegian champions in their first leg encounter at the Lerkendal Stadion last night.
Defender Frazer Wright netted after 19 minutes but Saints keeper Alan Mannus had to remain alert during a second-half bombardment that required a number of crucial saves to preserve their away-goal advantage ahead of next Thursday's return in Scotland.
But new boss Wright - who was in charge of the side for the first time since replacing Steve Lomas - insists his back-four and five-man midfield defended just as he had planned.
He said: "We were put under real pressure in the second half after controlling first-half and going in with a 1-0 lead at half time.
"We came here believing we could get a result and this was a game we deserved to win.
"We will probably go with the same game plan in the next match but the defenders, who had a brilliant game, will need to do the same again.
"Although we were threatened by them during the second half, our defensive plan worked out and showed what can happen if we play this way in the home leg.
"We knew we could set up some trouble for Rosenborg from set plays and Frazer got a great touch with the goal.
"Coming here to this stadium and winning is a magnificent achievement."
- Sports & Recreation
- Frazer Wright