You won't believe it when he rams in a tip-slam, his head hovering above the rim, as he did later in that game.
You will wonder, Where did he come from? when he runs 30 feet, appears out of nowhere and blocks a layup near the backboard square, the play that ensured the Hawks' A-10 title win over VCU on Sunday, Roberts' last game in conference play.
"That was a nice way to go out, huh?" he said afterward when asked about the block - after pretending to not remember it.
What you will not see if you keep an eye on Roberts is the posing, or the gesturing, or the self-congratulatory antics his teammates displayed in the A-10 final: the extended follow-through of Halil Kanacevic; the low "three" signs Langston Galloway flashes; the flexing of a questionable muscle set by freshman DeAndre Bembry.
St. Joe's coach Phil Martelli cannot stomach those sorts of displays:
"We don't need all those reactions. In fact, we are going to have a conversation with Langston going into the NCAA Tournament. You don't need all these gyrations, you know what I mean? They all come up with these special gimmicks for making a three-point shot. Make the three-point shot, and get on to the next play."
Martelli doesn't worry about Roberts' three-point celebration.
In 130 college games, Roberts has never even taken a three-point shot.
"I mean, it's just not something we need me to do," said Roberts, a 22-year-old with a 12-year-old's face. "Maybe it's something I'll work on to get to the next level."
With his bloodlines and his talents, Roberts will play at the next level, Martelli said. There, too, Roberts will be a joy to all who surround him.
He has been the Hawks' most improved player for the past three seasons.
Now a captain, he sets this sort of example:
The Hawks last week practiced at 10 a.m. on Tuesday for 2 hours.
At 2 p.m., Roberts was still in the gym.
Not only did no St. Joe's player miss a practice this season, no one was even late, a first for Martelli in his 19 seasons at St. Joe's.
"He understands that you have to give of yourself to be a part of something bigger than yourself," Martelli said. "Because of his willingness to accept coaching, he's one of those guys you wish you have the rest of your career."
Roberts' pedigree isn't bad, either.
His father and his mother met in Portugal while both were playing professionally. Ronald Sr., who played at Oklahoma, quit after 10 years as a pro in Spain, Portugal, Brazil and the Dominican Republic to move his wife, Dania, their four sons and two daughters from her native Dominican to Bayonne, N.J. She works as an accountant, he as a hospital security guard, and, in one of the nation's basketball hotbeds, they were eager for Robert Jr. to follow them onto the hardcourt.
He opted for the halfpipe. At the end of his freshman year in high school, he was a 6-6 skate rat who would rather watch the X Games than the Final Four.
"I mean, he just loved skateboarding. We were a little frustrated, but we never pushed him," his father said. "We always thought he should be playing basketball. We wanted him to love the game like we fell in love with the game. Now, he has."
Two of his brothers played briefly in junior college but, really, no one in the family got the height or the hops. Finally, as a high school sophomore, Roberts fell for basketball.
He averages 14.4 points and 7.4 rebounds per game and shoots 59.8 percent from the field, generally steady numbers since his sophomore season, when he was the Atlantic 10 Sixth Man of the Year. Then again, any sort of regression would not be tolerated at home, would it?
"My dad's not really on me like that. He doesn't get mad if I don't play well. He doesn't yell or whatever," Roberts said. "My mom is . . . more aggressive."
"Oh, I'm really bad," she admitted. "I'm the worst critic. I get on him for any little thing. I always tell him, 'You owe me a rebound!' When you know the game like us - when you actually see the next move, or what he did wrong, know that he should have moved a certain way - sometimes, those 2 hours of watching a game are terrible."
They are terrible hours, because they want their son to play perfectly; and they are wonderful hours, because they see one of their fine young sons thriving.
"They love their son," Martelli said. "They don't like their son because he plays basketball. Get this: There hasn't been a game in his 4 years where they haven't thanked me."
Perhaps, but still, they want their son to be more. He will graduate in the spring with a communications degree, "And that would be enough," his father said.
Not for the son.
"I do want to play professionally," he said. "And I want to play in the post, like I do now."
"We feel he can go really far. He's still missing a lot of things we're getting him to work on. Shooting and dribbling," said his father. "At this size, at the next level, he won't be able to play on the inside. We've got a lot of work to do."
Perhaps some scout will fall in love with Roberts in Buffalo, or, if the Hawks advance, beyond. Perhaps a scout will look at his father, who carries 280 pounds on his 6-8 frame, and see potential for Junior to grow into a post player.
Certainly, there will be plenty of eyes on Roberts tonight.
He's worth watching.
On Twitter: @inkstainedretch