Roccella phycopsis forms small, shrubby tufts up to about 5 cm tall. Each tuft is made of narrow that rise more or less vertically from the
substrate. At first the branches are round in cross-section, though they can become slightly angular or flattened with age, and their uneven, irregular pattern of forking gives the lichen a rather untidy appearance. Fresh material is a pale blue-grey or buff, while the inner body (the
medulla) shows a yellow tinge close to the base. Powdery reproductive patches called
soralia are plentiful: they start as tiny warts on the branch surface, then expand into globular, flour-like masses that shed microscopic particles for asexual dispersal and give older thalli a frosted look.
Sexual fruit bodies (
apothecia) are infrequent. When present they project conspicuously from the branches as rounded to elongated lumps, often twisted or misshapen. Unlike in many related lichens, the apothecia lack a rim of thallus tissue, so the whole is exposed and appears jet-black. Inside, the spore-bearing layer is threaded by support filaments () that remain unbranched at the base but divide near the tip. Each sac (
ascus) contains eight colourless
ascospores that become faintly brown with age; the spores are three-celled, straight to gently curved, and measure roughly 18–21 × 4–6 μm (occasionally as small as 14 μm long or as large as 23 μm). Tiny flask-shaped structures produce curved, rod-like
conidia 12–17 × about 1 μm, providing an additional means of reproduction. Standard chemical spot tests reveal a C+ (crimson) reaction in the outer cortex, no reaction in the soralia, and a blue-white
fluorescence under long-wave
ultraviolet light in the medulla, indicating
erythrin,
roccellic acid, and sometimes
lecanoric acid. ==Potential biotechnological uses==