The family name "Roman" may be derived from the Finnish place name Rauma, since Johan's ancestors lived in Finland.
Around 1715 the King granted Roman permission to study abroad, and the young composer spent some six years in London.
He almost certainly studied under Johann Christoph Pepusch, met Francesco Geminiani, Giovanni Bononcini, and, most importantly, George Frideric Handel, whose music made a lasting impression on Roman.
Roman's life during the 1720s was full of organisational activity which led to much improved standards at the chapel, and, in 1731, the first public concerts in Sweden.
In 1744 Roman composed one of his finest works, Drottningholmsmusique: a large orchestral suite for the wedding of the Crown Prince Adolf Frederick of Sweden and Louisa Ulrika of Prussia.
In 1745 Roman retired from his post as leader of the royal chapel due to deafness, which had progressed rapidly during the previous years.
Roman wrote this music for the wedding in August 1744 of the Crown Prince Adolf Frederick of Sweden and his bride Louisa Ulrika of Prussia.
Other pieces written by Roman include the suite of "Sjukmans Musiquen" and the Italian-inspired cantata Piante amiche.