He served in World War I in various capacities, rising to the rank of captain in the Polish army and earning a range of military honors.

[This paragraph needs citation(s)] Early in his childhood, De Rosen went to live with his two sisters, Maria and Zofia (she became a sculptor), in Paris, France, and it is said that he initially wrote poetry before deciding to devote himself to painting.

[2] Until 1921, De Rosen studied painting in Warsaw and had his first major exhibition the same year, while working for the Polish Foreign Affairs ministry.

In 1925 he had another major exhibition at Zachęta gallery in Warsaw, and upon seeing his religious work Armenian archbishop Józef Teodorowicz of Lwów asked him to paint the murals inside Lwów's restored Armenian Cathedral; he finished the work in 1929, along with another Polish artist Józef Mehoffer who painted the ceilings there.

[This paragraph needs citation(s)] Other murals and mosaics created by de Rosen may be seen at Other principal works by Jan Henryk de Rosen in the United States can be seen in Buffalo, Memphis, Pittsburgh, and in the California cities of La Jolla, Hollywood, Pasadena, Eagle Rock, Monterey Park, Vallejo and Sacramento.

[This paragraph needs citation(s)] Many of De Rosen's murals were in made wax tempera (a mixture of pigment and beeswax liquefied by alcohol) set in fields of gold leaf, on plaster.