Born in Viterbo to Laura de Angelis and Bartolomeo Romanelli, he went to Rome at age 14 to study to become an artist, and within a few years became part of the household of Cardinal Francesco Barberini. He was a pupil in the painting studio of Pietro da Cortona, the leading painter of his day, but the two eventually quarreled and so Romanelli left.
Romanelli was born in Viterbo to Laura de Angelis and Bartolomeo Romanelli, and at 14 he traveled to Rome to study art. He soon became a part of Cardinal Francesco Barberini's household and studied under the guidance of Pietro da Cortona, but their relationship ultimately ended due to disagreement.