But elation could so easily have been replaced by despair at the Stade Felix Mayol as the Parisian visitors led 19-11 at the interval and were on the brink of taking the game into extra time before Jonny Wilkinson slotted a match-winning drop goal with just 45 seconds left to play.
"We dug in and dug deep in the last 30 minutes," said Lewis-Roberts.
"We're pleased with the win - we worked hard and I thought we deserved it in the second half.
"We didn't ever think the game was beyond us. We had a chat at half time and we knew where we were going wrong. We worked hard on that and it paid off.
"It was a great win for us, particularly with that atmosphere in the crowd."
Toulon now turn their attentions to the May 18 clash with Biarritz Olympique in London as they look to finally bring a trophy to a club that has been seriously starved of silverware.
Biarritz beat Brive 19-0 to book their place in the final and, thanks in no small part to the pedigree of both teams and the passion of their support, Lewis-Roberts is expecting a huge encounter across the Channel.
"It will be a massive game when we go to The Stoop," added Lewis-Roberts, who is accustomed to playing at Harlequins' home ground having joined Toulon from Sale Sharks last summer.
"I think we all deserve a bit of silverware because we've worked really hard. We had a couple of bad games but we've started to put that right and things are beginning to pay off.
"This year we've shown that we've got a good team and a good squad and that's why we're pushing for both the Top 14 and the Amlin Challenge Cup.
"The move to France has been brilliant for me personally, I've really enjoyed it.
"I'm probably more suited to playing over here: it's all about the scrum and I think I've improved as a scrummager. Every game is a challenge and I've loved every minute of it."