The narrow leaves of Rosenia humilis are bluish grey and finely hairy. They are clustered near the tips of the pale grey stems that are bare lower down.

Leaf shape is linear to obovate. The leaf blades deviate in a variety of ways from straight and flat, by for instance being thick or three-sided and having a channel along the upper surface. The leaves become up to 2 cm long and 2 mm wide.

Young foliage is pale green, exuding a pine scent (Vlok and Schutte-Vlok, 2010; Shearing and Van Heerden, 2008; http://keys.lucidcentral.org/).