Johnson, a 6-foot-10 freshman center, who signed in May, scored seven of his team-high 19 points down the stretch to help undefeated FSU (6-0) equal its third-best start in school history.
While the Seminoles' schedule has been somewhat suspect in terms of quality, they still haven't started this fast in 15 years.
"This game was a tremendous test for us," Hamilton said.
""Ole Miss showed they obviously have a lot more experience than we do. They stuck with their game plan, even when they got down in the first half.
"I think they might have scored on seven straight possessions (during the second-half rally) and that's not something we're accustomed to allowing. They just did an outstanding job of rotating the ball and attacking the basket. Hopefully, we can take this game and learn from it."
Rebels coach Rod Barnes also was impressed with the Seminoles' effort. After making just one of their first 12 shots in the game, and shooting only 27-percent the first half, the Rebels were a different team in the final 20 minutes. But it still wasn't enough to overcome FSU.
"We had seven or eight kids on the team that have never been on the road before, so to come into this environment and play the way we did, I'm pleased," Barnes said.
"Leonard has done a great job with this program. Seeing how young his team is, they're only going to get better.
"I like Florida State's team because they can throw people at you. They can just keep coming and they keep coming and they keep coming. Obviously you have some that are better than others, but all of them are pretty much respectable players."
Hamilton, meanwhile, is increasing the minutes for Johnson, a nationally acclaimed post player, who grew up in nearby Albany, Ga.. Johnson was rated among the nation's Top 35 prospects by most recruiting services, after attending Bridgton Academy in Maine last season. He originally signed with Georgia when leaving high school in Albany, but failed to qualify.
"AJ has shown signs all year long that he's very capable of having this type of game,'' Hamilton said.
"Obviously he's rounding into shape, learning a defensive system, an offensive system, making adjustments to playing with his teammates, and it's been a little bit of an adjustment for him as I'm sure it is for many freshmen around the country.''
While off to its best start to a season since 1988, the Seminoles realize they still have plenty to prove.
``We feel like we haven't earned anything yet. We still have a lot of strong competition to go against,'' senior forward Michael Joiner said. ``[Ole Miss] was probably one of the strongest teams we've played.''
FSU is at home Saturday against Fairleigh Dickinson.