The vellum of the Voynich Manuscript has been dated to the first part of the 15th century, though it has been noted that the text could have been written later.
Roger Bacon, having lived in an earlier period is thus excluded from being the author of the VM.
There were a range of manuscript hands in use at the time - and a number of scripts (Latin, Greek, Cyrillic etc).
Prester John was believed to be in Africa in this period.
Early 15th century: beginning of Portuguese exploration and expansion - capture of Ceuta in 1415.
The Wikipedia page on the 15th century is .