A lot of people forget that Rocky deSantos was even a ranger, and that he was in the very first Power Ranger movie ever made. He wasn’t even in “Forever Red”, the episode when all of the previous red rangers returned. Of course, he will never be a ranger the way Jason was a ranger, but he was never meant to be.
Rocky isn’t meant to be Jason, even though he replaced him. He is his own character. We rarely see Jason’s strengths in school. He is known more for his physical abilities and his ability to be a leader. Rocky is a calm medium between Jason and Billy. You can see he is smart in school, but not a genius, but he is also known for teaching karate lessons (most of the male rangers are during this point, with the exception of Billy).
The red ranger usually has the association with the leader. This has been the case for many of the seasons in Power Rangers. Mighty Morphn Power Rangers is the only series that has a ranger leader that is not red. This change happened when Jason was still a ranger. This obviously created some tension in between him and Tommy. After Tommy became the leader, there were still moments when Jason would lead the group. When Rocky enters the picture, that is not there anymore, and this is one of the biggest criticisms that Rocky gets as a ranger.
However, it was never Rocky’s place to be the leader. He was the newcomer in the group and was assigned to follow under Tommy, and there was no reason for him to dispute that. He was never given the opportunity to be the leader, so he simply did not rise up to be one. He did, however, fulfill his role as a part of the ranger team.