This Anglo-Norman text seems to have borrowed a dative or ablative form from Latin, rather than the more common nominative ros marinus, cf. rosemarin.
s.
rore marino
1bot.rosemary, perennial herb with fragrant, needle-like leaves, Rosmarinus officinalis:
(
s.xiii2/4; MS: s.xiii3/4
)
Moille l'en le devant dite pain en aisil et le trible [l'en] avesques rore marino ou ovesques flors de rore marino, si l'en les porra avoir
i 209
rore1 (s.xiii2/4)