In 1582 Gruffydd Robert requested retirement from publicly preaching in the cathedral of Milan; there being no other position vacant, he received a diocesan pension.
The first part of Gruffydd Robert's groundbreaking grammar of Welsh was published as Dosbarth Byrr ar y rhann gyntaf i ramadeg Cymraeg ('A brief analysis of the first part of a Welsh Grammar') in Milan on Saint David's Day in 1567, probably at the press of Vincenzo Girardoni.
All of these are presented in the form of a dialogue between Gruffydd and Morys Clynnog, described as having taken place in a vineyard (possibly at Monti di Creta in Rome, which belonged to the Hospice).
Clynnog himself is reported as having drowned c. 1582; St. Carlo Borromeo, who is referred to as Gruffydd's master or lord in the grammar, also died in 1584.
Also included with the grammar were the first published collection of Welsh poems and what remains of Gruffydd's literary translation of the Cato Maior de Senectute by Cicero.