Rama and Krishna belongs to tretha and dwapara yuga respectively.
Mahabharata has statements about Rama, told by Hanuman, rishi's etc., So it can be inferred that Lord Rama was well known at the times of Krishna.
But is there any statement from any scripture by Krishna about Rama?
Yes he did.
https://www.sacred-texts.com/hin/m09/m09031.htm
Similarly was the Rakshasa Ravana of Pulastya's race, with his relatives and followers, slain by Rama!
Krishna consoled Yudhisthira when he was in grief of the death of his kinsmen and told how Dasaratha's son Rama also fell prey to death.
We hear, O Srinjaya, that Rama also, the son of Dasaratha, fell a prey to death. He always cherished his subjects as if they were the sons of his own loins. In his dominions there were no widows and none that was helpless. Indeed, Rama in governing his kingdom always acted like his father Dasaratha. The clouds, yielding showers season ably, caused the crops to grow abundantly. During the period of his rule, food was always abundant in his kingdom. No death occurred by drowning or by fire. As long as Rama governed it, there was no fear in his kingdom of any disease. Every man lived for a thousand years, and every man was blessed with a thousand children. During the period of Rama's sway, all men were whole and all men attained the fruition of their wishes. The very women did not quarrel with one another, what need then be said of the men? During his rule his subjects were always devoted to virtue. Contented, crowned with fruition in respect of all the objects of their desire, fearless, free, and wedded to the vow of truth, were all the people when Rama governed the kingdom. The trees always bore flowers and fruit and were subject to no accidents. Every cow yielded milk filling a drona to the brim. Having dwelt, in the observance of severe penances, for four and ten years in the woods, Rama performed ten Horse-sacrifices of great splendour and to them the freest access was given to all. Possessed of youth, of a dark complexion, with red eyes, he looked like the leader of an elephantine herd. With aims stretching down to his knees and of handsome face, his shoulders were like those of a lion and the might of his arms great. Ascending upon the throne of Ayodhya, he ruled for ten thousand and ten hundred years. When, he O Srinjaya, who transcended thee in the four principal attributes and who was purer than thy son, fell a prey to death, do not grieve for thy son that is dead.
Yes, Shree Krishna talked about Shree Rama in Srimad Bhagavad Gita 10.31. While giving a discourse to Arjuna. Krishna reveals his divine being in greater detail, as the ultimate cause of all material and spiritual existence, one who transcends all opposites and who is beyond any duality. Krishna says he is the atman in all beings.
पवनः पवतामस्मि रामः शस्त्रभृतामहम्।
झषाणां मकरश्चास्मि स्रोतसामस्मि जाह्नवी।। 10.31 ।।pavanaḥ pavatām asmi rāmaḥ śastra-bhṛtām aham
jhaṣāṇāṁ makaraś cāsmi srotasām asmi jāhnavīOf purifiers, I am the wind, of the wielders of weapons I am Rāma, of fishes I am the makaraḥ, and of flowing rivers I am the Gaṅgā.
10.31 Pavatam, of the purifiers; I am pavanah, air. Sastra-bhrtam, among weilders of weapons, I am Rama, son of Dasaratha. Jhasanam, among fishes etc; I am the particular species of fish called makaraḥ. I am jahnavi, Ganga; srotasam, among rivers, among streams of water.
Here in this verse, Shree Krishna is talking about Shree Rama. He is indirectly telling Arjuna that among the wielders of weapons Rama is the best and "I am Rama, son of Dasaratha." i.e. we both are same.
