The rose is one of the small number of plant attributions that is genuinely classical rather than Renaissance. It is Venus's flower in Greek and Roman literature centuries before any planetary herbal existed.
The mythological accounts vary, which is itself informative: the rose springs from the blood of the wounded Adonis, or from Aphrodite's own blood as she runs through thorns to reach him, or from the foam of her sea-birth, or it is stained red by her blood from white. Multiple incompatible origin stories for the same association are a sign of a cult fact looking for a narrative, not of a narrative generating a cult fact. Roses were used in Aphrodite's worship and at Roman festivals; the Rosalia was a genuine calendar observance of decorating the dead with roses.
Culpeper repeats the attribution and specifies the red and damask roses. He is not the source and does not claim to be.
The rose then acquired a second, competing symbolic career in Christian usage, as the flower of the Virgin. The rosary takes its name from a garland of roses, the enclosed rose garden of the hortus conclusus is a Marian image, and the rose window is a standing feature of Gothic architecture. This is a deliberate reassignment of a pagan symbol rather than an accident, and the two readings, erotic and virginal, sit on the same flower throughout medieval European art, sometimes in the same picture.
Sub rosa, under the rose, meaning in confidence, is Roman: a rose hung above a table marked what was said beneath it as not to be repeated.