... especially as that obsolete initial 'y', equivalent of later suffix -ed to imply adjectival participle, gives one that final letter of 'rosy'. "Like a rose fair" would make good sense, given poetic inversion of noun & adjective. But "like a rosy fair" must be a garbled form of something; so where might that final 'y' have floated in from?

Speculation? Maybe. But think of interpretative implications, even so.

≈M≈