The epithet, rosei, is in honor of Joseph Nelson Rose who collected the lichen on San Roque Island, 15 March 1911, during the Albatross Expedition.

[1] His lichen specimens had been kept separate from the mounted and filed lichen collections in the herbarium at the Smithsonian Institution, Department of Botany, US)[2] loose in brown standard herbarium paper, and were made available to Richard Spjut sometime after 1986 while he was undertaking a revision of the genus Niebla.

Vermilacinia rosei is classified in the subgenus Vermilacinia in which it is distinguished from related species by its thallus divided into relatively few fan-shaped branches (less than 10)—widely expanded above a short narrow stalk-like base—and by its secondary metabolites of triterpenes, referred to as T1 and T2 by their Rf values on thin-layer chromatography plates; their formulas are C30H50O2 (T1) and C30H50OO (T2).

Lichen substances also include the triterpene zeorin and the diterpene (-)-16 α-hydroxykaurane that characterize subgenus Vermilacinia.

[3] A specimen from Cedros Island referred to this species, collected by Richard Spjut and Richard Marin in April 1990, differs by having a thicker reticulate ridged cortex, 75–110 μm thick, compared to the cortex in the type collection with crater-like depression, 45–65(-75) μm thick.