Illustris uiri D. Ioannis de Roias Commentariorum in astrolabium quod planispha︠e︡rium uocant
Subtitle: libri sex nunc primùm in lucem editi. His additus est index capitum ac rerum, qua︠e︡ toto opere continentur, locupletissimus
Publisher: Apud Vascosanum
Published: 1550
Place of publication: Lvtetiae
Language: lat
Number of pages: 282
Notes: Pages 30, 31 and 238 incorrectly numbered 31, 32 and 248 respectively.

Describes two varieties of an astrolabe devised by the author.

Book V is a chapter-by-chapter commentary on Gemma Frisius' Libellus de locorum describendorum ratione.--cf. Pogo, A. Gemma Frisius (Isis, v. 22, p. 479-483)