Michael Carrick's side impressed in Norway, especially young Jaydan Kamason, who replaced Harry Maguire at halftime.
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Manchester United have won their second match of pre-season against Rosenborg in Trondheim, Norway. Michael Carrick's side netted five goals and kept a clean sheet after a disappointing loss against Wrexham last week.
Unlike the first match, the majority of United's starting side remained on the pitch for 60 minutes, although Harry Maguire and Luke Shaw made way at halftime for Harry Amass and Jaydan Kamason.
Kamason has been mentioned as a promising right-back at United for several years, but had not been given his opportunity until this pre-season.
Against Rosenborg, Kamason registered two assists from the bench and looked an attacking threat through his half, despite not having a natural right-winger ahead of him.
The majority of the side after the 60-minute set of changes was made up of Manchester United's Under-21s, although some more senior players (Toby Collyer and Tyler Fletcher) were also involved.
"The younger players, [it's great] when you see them expressing themselves and being themselves and keep pushing themselves to be better," Carrick told MUTV after the match.
"I think some of the play in the second half was really, really good, and I was delighted to see that from them because they've all got potential in different ways and you want them to fulfil it and keep pushing themselves, and they certainly did that."
Carrick also ensured to keep fans grounded after United's difficult start to the match before Shea Lacey's opener in the 31st minute.
"It's never going to be perfect," he said. "We're two weeks in and you're kind of building towards that.
"So I thought there's a lot of good things. Some of the goals were fantastic goals and just as pleasing to keep a clean sheet."
Jaydan Kamason was involved in two of the goals during the second half. For Harry Amass' finish, he delivered a brilliant ball into the box from the right flank, while for Williams' goal, he drove inside before playing it across the six-yard box for Williams to tap home.
With most of United's senior players still on their break after the World Cup, Jaydan Kamason will likely stay involved with the first-team pre-season for the time being.
When Diogo Dalot and Noussair Mazraoui return, Kamason may drop out of the side, but could continue to travel with Michael Carrick's group for senior experience – something which will be more likely if he continues to impress.
However, during the season, Kamason may look for his first loan move away from Old Trafford. United will likely be targeting clubs in League One and Two, but could also use INEOS-owned Lausanne-Sport, as they have with Sékou Koné.
Kamason's main focus for now will be continuing to help the senior side, who are in a "good place" according to Michael Carrick.
He said: "I think we're in a good place. Four weeks to go until the start, gradually getting some boys back from the World Cup as we progress.
"Moving forward, it's a really good direction to go in."