Then he was assistant at the Vienna University of Technology, where he attained the Habilitation in 1910.
In 1913 Rothe married and began to teach mathematics at the Vienna University of Technology as Professor extraordinarius, and from 1920 as Professor ordinarius.
[1] Rothe is known for his collaboration (1910–1912) with Philipp Frank on special relativity.
Based on group theory, they tried to derive the Lorentz transformation without the postulate of the constancy of the speed of light.
[2] Furthermore, Rothe worked — outside his teaching activity — on mathematical problems like Hermann Grassmann's "Ausdehnungslehre" (theory of extension, or exterior algebra).