I'm not sure there's much that can be said here. With the breakdown of the Roman education system in broadly the sixth century, systematic knowledge of Greek more or less ceased in the west. So, from this point onwards, untranslated Greek texts were, as a rule, not used in the Latin world. The only authors who remained accessible were those who had been translated into Latin and the Greek to Latin translations that did occur in the Early Middle Ages, such as those of Eriugena, were primarily Greek patristics/Christian neoplatonic texts like Gregory of Nyssa, Maximus the Confessor and Pseudo-Dionysius.

Medieval platonism was more generally grounded in the writings of these Patristic and Christian neoplatonic authors than engagement with Plato directly. Indeed, the platonism of Augustine himself was, as far as I'm aware, more heavily influenced by the late-antique neoplatonists like Porphyry and Plotinus, than direct engagement with Plato's own writings. And indeed the prevailing trend of late-antique neoplatonism was broadly embedded in the writings of Christian authors of this period.

But to the question at hand, prior to the twelfth century, the only non-Christian greek philosophical texts available were those already translated into Latin in antiquity/late-antiquity. The primary source for these is, of course, Boethius who, besides translating the majority of Aristotle's Organon (save the Posterior Analytics), also translated Porphyry's Isagoge. Other than this, the only text of Plato, for which a Latin translation survived, partially by Cicero and the more completely by Calcidius, is his Timaeus. Homer was not read in the Latin Middle Ages. Knowledge of Homer was drawn indirectly through classical Latin authors like Vergil, through the common Latin prose history of the Trojan war (the De exidio troiae of Dares Phrygius) or the extremely abbreviated Latin adaptation (the Ilias Latina). Finally, Euclid was translated in the 1120s by Adelard of Bath, in the 1140s by Herman of Carinthia and once more in 1187 by Gerard of Cremona, all from the Arabic. (I don't know off hand the relative significance of these translations as compared with one another.)