I'm unsure of what sort of pairing you are interested in, but needless to say, there was a large diversity of relationships that aren't captured by the stereotype that Greek men and freeborn boys engaged in a pedagogical pederasty, and Roman men and slave boys engaged in sex. Responses to all these activities varied as well, but then even the "prevailing" culture in Greece of pedagogical pederasty wasn't universally accepted. Let me also quickly note that as far as Greek pederasty is concerned, the notion of penetrator/penetrated, and even the often associated active/passive dichotomy isn't particularly relevant.

We have documentation of same-sex physical activity or admiration between equal aged youths:

Theognis 1063-1064

"In youth you can sleep the night through with an equal-aged friend,
Unloading the desire for lusty action,"

Theognis 1319-1320

"Boy, since the goddess Cypris gave you a lusty
Grace, and your beauty’s every boy’s concern,"

Pindar Tenth Pythian Ode

"I expect by my songs to make the crowned Hippocleas
Still more splendid to look upon to both his age-mates and older men,
And a heartthrob for young maids. For
Different loves tickle the fancies of different folks."

Alcman, First Maidens’ Song is believed by some to be an initiation rite for two women.

Plato, Charmides

"But even so, at the moment Charmides came in he seemed to me to be amazing in stature and appearance, and everyone there looked to me to be in love with him, they were so astonished and confused by his entrance, and many other lovers followed in his train. That men of my age should have been affected this way was natural enough, but I noticed that even the small boys fixed their eyes upon him and no one of them, not even the littlest, looked at anyone else, but all gazed at him as if he were a statue."

Xenophon, Symposium

“Do you not see that the soft hair has recently crept alongside this one’s ears, while it already climbs from Cleinias’ chin towards the back. Critobulus here was mightily inflamed before, when he went to the same school as Cleinias,"

In terms of relationships between older individuals:

It's been reported that the adults of Agathon and Pausanias were lifelong lovers.

Stoics were accused of keeping boyfriends to the age of twenty eight.

Aristotle, Nichomachean Ethics

"For lover and beloved do not take pleasure in the same things: rather, the lover takes pleasure in gazing at his beloved, while the latter takes pleasure in the attentions of his lover. But when the beloved’s youthful beauty fades sometimes the friendship too fades. For now the lover does not find the boy pleasing to look at, and the boy receives no attention. But many couples continue the relationship, if, as a result of spending time together, they come to love each other’s character, because they are of similar character."

Philostratus

"Why do you show me your beard, my boy? You are not ending your beauty, but starting it. For although the peak of your youthful season, the part that is flighty and untrustworthy, has passed and is extinguished like a burst of flame, the settled and secure part remains. Time does not embarrass the truly beautiful, but shows them off and bears witness to them more than it begrudges them. Homer, a poet who knows how both to observe and to write about beauty, says that the bearded man is the most lovely.119 He would never have revealed this unless he himself had first touched and kissed the beard of a beloved. For before they bloomed, your tender and radiant cheeks did not differ from a woman’s. But now that you are downy, you are more manly and perfect than your former self. What? Did you want to be no different from a eunuch? Their chins are barren, hard, and stony. These tainted men are at any rate more ashamed of this razor than that one,120 considering that a secret, this a clear and visible sign of their condition"

Here's an example in which the roles were reversed from age:

Xenophon, Anabasis:

"While still at the peak of youth and beauty, he obtained from Aristippus the command of his mercenaries and got on very intimate terms with the barbarian Ariaios, because Ariaios enjoyed the company of beautiful youths; he himself, although beardless, had as his boy love Tharupas, whose beard was already grown."

I highly recommend looking through if you have the chance: "Homosexuality in Greece and Rome: A Sourcebook of Basic Documents." It's introduction serves nicely in detailing the variety of relationship types that existed, and combating some myths.