O Rosa Bella is a popular 15th century chanson, originally attributed to John Dunstable, but now to John Bedingham (see say the article by David Fallows, [1]). It is based on a poem written by Leonardo Giustiniani (1388-1446)
The text of the first verse is:
Stanley Sadie in the Cambridge Music Guide gives as translation:
The chanson was used as a basis for several other works, including that by Ockeghem, and masses attributed to Gilles Joye; however, Johannes Ciconia's early version shares the words but not the tune (see e.g. [2])
See midi and nwc2 versions with text on the ChoralWiki site [3].
(Arte Nova 59210)