Sandercock handed his new signing his Super League debut in the 34-29 defeat at the KC Lightstream Stadium.
Ulugia, who turned 22 yesterday, started and lasted 46 minutes before being replaced at right centre by Graeme Horne.
Sandercock was pleased with the Kiwi's contribution, but accepts work needs to be done on his fitness before he can play the full 80 minutes.
"We knew Wayne had a lot to do on his fitness," he told the Mail.
"The plan was to give him 50 or 60 minutes and we'll sit down and have a good think about this Salford game.
"We need to do what's right for the boy to make sure he's as fit as he can be to put his best foot forward.
"In saying that, he showed some really good signs and class touches.
"It's a balancing act between playing the kid, although we don't think he's 100 per cent fit, or do you play him because he gave us some real class out there?
"I'll have to think carefully about that one."
Ulugia came in for Liam Salter, who Sandercock felt needed a well-earned break.
The young centre had played all but the season opener against Leeds and had taken to the field through the pain barrier.
Sandercock said taking Salter out of the team was to give him time to recover from recent injuries.
"Liam has copped a lot of bangs in recent weeks," he explained.
"He is still recovering from a dead leg. He's only 20 and he needed a break. He's a very courageous young man.
"Wayne is a good player and we didn't bring him all the way over here for nothing.
"But we need to be comfortable with ourselves that he can get through 80 minutes.
"If he does play, that's what he needs to do."
Sandercock will be able to call on the majority of last week's squad that lost to Widnes.
Prop Jonny Walker sits out the trip to the AJ Bell Stadium after entering an early guilty plea to a charge of dangerous contact against Ben Kavanagh, with Jason Netherton returning.
It's the third different Rovers player and the fourth suspension handed down to a KR player this season.
Sandercock believes Walker was hard done by considering other tackles that have gone unpunished this week and has once again called for consistency throughout the game.
"Consistency is a big thing in our game whether it's referees, players, the judiciary process or the match review committee," Sandercock said.
"All clubs are after is consistency.
"I could show you 20 tackles from the weekend I consider worse than the one Jonny got charged with.
"Nothing happened to them and that's why our club is frustrated."
KR 19-man squad: Burns, Cockayne, Costigan, Cox, Gardner, Green, Hall, D. Hodgson, J. Hodgson, Horne, Keating, Larroyer, Langley, Lovegrove, Netherton, Salter, Ulugia, Welham, Weyman.
