[3] Its scientific name is a testimony to Mr. W. F. H. Rosenberg who collected the type series,[2] and its common name refers to the aggressiveness of males of the species.

Its skin is granulated with small warts, and yellowish, greyish, or reddish in colour, with brown or blackish marbling or spots.

[2] It also has dark worm-like markings across the dorsal surfaces of the body and limbs, with gray-white undersurfaces and a pigmented area that covers near the throat.

[6] In addition, the female's body wall in front of its groin is nearly transparent, a feature that allows its black eggs to be easily seen.

[6] Females also possess these spines, though they are very small, and only males have control over its position and the ability to retract its fleshy sheath to reveal the scythe-shaped parts for combat.

[6] H. rosenbergi inhabits primary and secondary forest, as well as in heavily altered areas such as small strips of trees in pastureland.

[9] It is sympatric with H. boans and sometimes H. pugnax, and co-occur with both of these species in the headwaters of Rio Sinu and in Parque Nacional Natural de Katios in the northern Choco region of Colombia.

Reproductively mature frogs do not grow during the breeding season, this is due to increased energy expenditure rather than food shortage.

[6] Tadpoles of H. rosenbergi undergo metamorphosis at a size of 21mm SVL, approximately 40 days after fertilization, resulting in extremely large fat bodies and visibly undifferentiated gonads.

[6] These froglets are covered with many small dark spots and have much less webbing in the fingers and toes as compared to adult frogs.

Females of the species have been found to be influenced by the social cue of the current chorus size in moderating their reproductive activity, while males have been found to be influenced both by same day precipitation (with heavy rainfall decreasing activity) and previous day chorus size.

[6] For clutch guarding, males will sit on a perch near or immediately above a freshly laid egg monolayer, remaining silent except for infrequent territorial calls.

[6] While aggression from males is implicit in the English name of this species, male-male aggression and combat has only been observed in the Panamanian population of the species, not the Costa Rican one, likely due to the abundance of nest sites and low density of reproductively active males in the Costa Rican population.

[6] Violent aggression also involved growling and hissing and the use of unsheathed prepollical spines, and can result in serious wounds or death.

It also is a large energetic cost for males who fight and typically forces them to leave the breeding area or it results in them being unable to call to find a mate.

[6] Predators of H. rosenbergi include snakes (such as Leptodeira annulata), other frogs (such as Leptodactylus pentadactylus) and possibly mammals and crocodiles.