It is not just a reversal of role but the change of times, that is also important. Each Yug has its own dharma. What is applicable in one Yuga is no more fully applicable in another Yuga. Lord Rama came at a time when the Asuric Maya, the brute beast and the devouring Rakshasa were ruling the world. He had to tame the beast and annihilate the Rakshasa, set the highest standard of Rajdharma wherein the king acts according to the prevalent law so as to set the highest standard of public probity. Hence he acted like a strong ruler and a mighty king but without letting his personal emotions overpower his sense of duty and a human righteousness that is always an imperfect tool. Yet that was the best for his Age.
Sri Krishna came when the Asuric Maya and the Rakshasa were not so much outside but within man as gigantic egos and inordinately ambitious kings. He had to find a way to ensure that India is safe in the hands of a righteous emperor and set an example of living normally in freedom and delight. He did not come to establish the ideal of a righteous man but of a man who is inwardly, spiritually free and yet engaged in action with the purpose of carrying the march of humanity forward. Therefore we see in Sri Krishna’s action a certain largeness and freedom whereas in Lord Rama a certain restriction and righteousness. Both restored the dharma and set new standards for their times. Both acted selflessly without any personal interest. Both were ahead of their times and hence misunderstood even though worshipped. And they continue to be misunderstood because man judges by his own narrow yardsticks. Because almost all human beings act driven by personal egoism and seeking for personal gains, pleasures and desires, they find it difficult to understand the action of the Divine beings for whom the greater, larger good is much more important than writing a name for themselves or catering to the common public opinions of the average humanity.
As to specific instances in their life, I think we have written about it in some detail. But will be happy to answer if there is a specific question behind this one which is more of a general nature.
Affectionately,
Alok Da