Stenogyne rotundifolia is a scandent vine that can climb up to 5 meters tall. The stems are notably sharply 4-angled and range from densely hispid to moderately so, with hairs concentrated along the stem angles. It features simple, opposite leaves with suborbicular blades measuring between 1.9 to 5.2 cm in length and 1.9 to 4.5 cm in width. The leaf apex is typically obtuse, though occasionally acute, and the base ranges from cordate to occasionally truncate. The leaf surfaces are either glabrous or sparsely hispid, and the blades are membranous. The margins are serrated, and the 6–18 mm long petioles are moderately hispid. The flowers are arranged 6(–8) per verticillaster (inflorescence that resembles a whorl but consists of two crowded cymes on either side of the stem) and are axillary, with pedicels measuring 4–6 mm long that are also hispid. The calyx is weakly bilabiate and campanulate, measuring 6–11 mm in length, and enlarges as the fruit develops, showing sparse pubescence near its base. The corolla, bilabiate in structure, varies in color from cream to pale pink distally and is very densely pubescent externally while being glabrous inside. The corolla tube is narrowly funnelform, slightly falcate, and measures 15–21 mm long. It features an upper lip 4–9 mm long and a lower lip approximately 3 mm long with three lobes. The stamens, which are four in number, are inserted near the throat of the corolla and are pubescent. The superior ovary is divided longitudinally into two carpels, with one ovule per ovary lobe, and leads to a style that is usually cleft and exserted. The fruit is a drupaceous nutlet (pictured), approximately 3 mm long, black at maturity, and with slightly winged margins. The fruit is obliquely attached at the base and remains within the calyx at maturity, with a fleshy and obovoid exocarp. The seeds lack an endosperm or are scanty, oily endosperm. It inhabits wet forests between 1,800-2,150 meters.