Roberts was fond of architectural subjects, and produced a number of studies of Edinburgh's buildings. He then joined a travelling theatre as a scene-painter and travelled the country. In 1823 he went to London and worked on sets for the Drury Lane Theatre, and then on to Covent Garden.
In 1824 he was admitted to the Society of British Artists, and later that year he travelled to Normandy and painted a large number of Gothic period buildings.
Roberts developed a love of travel and journeyed across Europe to Syria and Egypt, where he painted an extensive collection of the stunning water-colours for which he is best-known today. Around this time he became interested in lithography and he made a number of lithographs of his own paintings, which were widely distributed and which proved to be extremely lucrative.
Roberts also became an important landscape artist. From 1838 his work influenced the 19th century Dutch painters, with his fabulous use of the colours and styles which were an assimilation of his European training and his later Oriental influences.