Lewis & Short

rŏsāles escae [rosa], an annual feast, when the tombs were adorned with garlands of roses, the feast of roses; cf. our Decoration day, Inscr. Orell. 4419; cf.: ROSAE ET ESCAE, ib. 4418.
The ceremony of hanging up the garlands was called ROSALIA, ĭum, n., Inscr. Maff. Mus. Veron. 146, 3.