The 21-year-old chose an important moment to score his first league goal for the club in south west London as his second-half strike gave the Millers a 1-0 win and extended their lead at the top of League One to nine points.
Kayode, who spent last season on loan at Carlisle, has had to be patient to get his chance as he has been behind Michael Smith, Freddie Ladapo and Will Grigg.
But with Ladapo out in the cold following his January transfer request and Grigg picking up an injury, it could be Kayode’s moment.
“I am over the moon for JJ to score a big boy goal,” boss Paul Warne said.
“It's brilliant for him, I'm really pleased.
“There is no better feeling for a striker to get a 1-0 win and it's your goal, you get all the headlines.
“It's very difficult to get into this team, it is hard work to stay in the team.
“For him to come on and get his goal is great. He is a goal threat.
“We spend all of our time shouting at him, but he is improving, he is fortunate that he is in a group of very good strikers so he is learning every day.”
The win on Rotherham’s first visit to the new Plough Lane Stadium was not a classic but could be vital come the end of the season.
The Millers were the only side in the top six to win as they gave themselves breathing space at the summit of the table.
If they can come through games against Sheffield Wednesday and Wigan in the next week then automatic promotion looks a certainty.
“It was OK,” Warne said of the performance. “They are really well organised, they are hard to break down, they pick up midfield pockets but on the whole I thought we were the better side.
“I thought we deserved more than 1-0. We had the goal disallowed in the first half.
“A good away performance, another clean sheet, we have only conceded five goals away.
“From the outset we tried to win the game, draws are no good to us.
“We tried to grab the game by the throat and we did really. We created enough chances to win and I think we deserved it.”