The wood vessels have very oblique oval openings which are subdivided by about 20 (maximally 50) bars (this is called scalariform), while the side walls have pits in rows and lack spiral-shaped thickenings.

The pollen grains are circular, 25–30 μm in diameter, secreted in a wet, sticky, yellowish fluid, which easily attaches to smooth surfaces.

Since the development of methods to compare DNA to determine relationships between organisms (phylogenetics), the affinities of Roussea to the Asterales have been affirmed repeatedly.

[4] Phylogenetic analysis puts a clade consisting of Abrophyllum, Cuttsia and Carpodetus in the subfamily Carpodetoideae as sister to Roussea, on its own representing the Rousseoideae.

[6] Roussea simplex is an endemic climbing shrub of Mauritius, currently known to be confined in nine locations around the south-east, centre and south-west regions of the island.

[7] This climbing shrub mainly grows in wet, high elevation cloud forests, such as at Le Pouce, Mauritius' third highest mountain .

[9] More recently, the Mauritius bulbul, Hypsipetes olivaceus was revealed as a more efficient pollinator of Roussea given its long beak and ability to fly longer distances.

[10] Technomyrmex albipes, a small ant introduced to Mauritius that came originally from the Indo-Pacific area, seals the flowers of Roussea with clay to protect mealy bugs.

The ants attack animals that visit the plant, and so prevent the blue-tailed day gecko from pollinating the flowers and from eating the fruit, and in this way seriously hampering the reproduction of Roussea.

[9] Two new species were reported to visit flowers for nectar, the native Plagiolepis madecassa[11] and the invasive yellow crazy ant, Anoplolepis gracilipes.