The word is used in Continental French (DMF: ‘petit robe (ou robe misérable)’), but its sole attestation in Anglo-Norman is problematic.
This passage translates the Vulgate’s ‘et specula et sindones et vittas et theristra’ (Isaiah 3:23). The term theristrum (DMLBS 3433b) refers to a sort of light garment typically worn by women. Thus, robete can be interpreted as a diminutive of robe1, referring to a small cloak or shawl.
However, grammatically bende de robetes, with the preposition de rather than et, is harder to explain. Interestingly, the alternative manuscript (B) reading provides an entirely different translation: ‘gerlaundes filees [...] de [...] perles precious’, with the entire clause translating only vitta (‘woman’s hairband or tiara’) and omitting any reference to theristrum. This alternative reading, together with the use of the preposition de, suggest that robete may have to be interpreted differently. The word could also be read as a vernacular form of Latin rubetus: ‘red jewel, ruby’ (cf. DMF rubiet), with vittas translated as ‘band of rubies’ and theristra again left untranslated.
In that case, manuscript A is most likely already a corruption of an unattested, but Biblically correct, bendes et robetes reading, providing an etymologically entirely different interpretation, which is echoed in manuscript ‘B’.
In conclusion, the two etymologies provide a single homonym in Anglo-Norman, and the sole attestation of it appears to support both interpretations.