All three made the bench for the 4-0 victory, with Thomson and Roberts making their maiden appearances in a first-team matchday squad of 18.
Mulholland explained: “Liam made his debut on the Tuesday night against Raith Rovers, and when he came into the Academy on the Wednesday, all of the young players were absolutely buzzing, and the staff were the same.
“Many of the staff are working 60, 70 and 80 hour weeks, but it makes it worthwhile when you see that happening.
“For the young players, to have that aspirational bit and that pathway to the first team, despite being a massive football club, that pathway is fairly unique, and it is credit to the manager, David and Frank McParland that they are allowing them to do that.
“The boys need to be good enough, but certainly it was a major, major boost seeing the boys on the bench.”
Mulholland also reckons their experience in the top-team will stand them in good stead when they return to their respective youth teams.
He added: “I spoke to the boys on Monday and they had so many ideas they had learned from the first team on analysis, how they prepare for the game and information the manager had given them.
“So if that helps them come back here and play with the under-17s or under-20s, then great, and every boy that comes through here must be hungry and desperate, and when you get a taste of that you want to experience it again and again.”