Reilly was appointed to the Roscoe Chair of Architecture in 1904 at the age of 30, quite shortly after he had become an associate of RIBA in 1898, leaving him little time in which to build substantially. His partnership with Peach had given him a limited amount of practical experience, but apart from this Reilly's major works (such as the Liverpool Cathedral design) were all on paper, and were destined to remain so. What little work Reilly had in progress at the time of his appointment consisted of a scheme for a generating station, laundry and associated buildings for Lord Newton, at Lyme Park, Cheshire in 1904–1905, which it seems he had brought with him from his partnership with Peach. The designs are firmly within the Arts and Crafts tradition, and as it is well-evidenced that this was not to Reilly's taste, we can assume he was following the specific requirements of his patron, Lord Newton. The scheme figures heavily in Reilly's early correspondence books. In a letter to the Vice- Chancellor of Liverpool in the early months of his appointment, Reilly astutely makes the most of his meagre practical work and mentions the scheme as a good example to his students of ‘real work in the course of execution’. He thought it important for the students to see such work undertaken by their professor.

Other schemes from around this time include plans for a new building to house the Faculty of Arts and Fine Arts. This was intended to form part of the plan, devised by Reilly and other members of the New Testament group, to found a number of chairs in fine art, music and so on, which major practitioners would be invited to take up. The faculty buildings planned by Reilly were sited, well away from the main university campus, in the Haymarket district near to the city's museum, library and art gallery. He wrote that he had envisaged that the library would become part of the university, along with the art collection and museum, forming part of its learning resource. The scheme came to nothing; following consideration by the City Council, in an education committee report of 1904 it was felt that it would provide too much competition to the newly formed and expanded School of Art.