We have had many expansions to the abbreviation of RRR but Roudram Ranam Rudhiram is the official title that SS Rajamouli and team selected for the film.
Seems like it is a battle of Hot headed Ramaraju played by Ram Charan, symbolized by fire and cool and calculative, Bheem played by Jr. NTR, symbolized by water.
The title can be explained further as the angst caused by oppression, slavery inflicted by British Empire on Indians leads to great amount of anger which then turns into a war against them lead by these two youngsters.
As war leads to blood, Rudhiram is used. Rudhiram also means boiling blood and blood bath. Seems like SSR gave away first, second and third acts of the film in the title, itself.
Finally, we have a confirmation on the title and the characteristics of the two leads as well. This might be another epic addition to SSR's already accomplished filmography!