[2] Here he was influenced by William Abel Pantin and E. F. Jacob, who helped Roskell gravitate towards medieval history.

[2] Roskell was taught a neo-Stubbsian method that sought to use administrative and biographical research in studying constitutional history.

His master's thesis was published by the Chetham Society in 1937 as The Knights of the Shire for the County Palatine of Lancaster, 1377–1460.

[1][2] After being awarded a Langton Fellowship in 1935, Roskell studied the Parliament of 1422 at Balliol College, Oxford, for his doctoral thesis.

[2] Against the views of Albert Pollard and J. E. Neale, Roskell argued in 1964 that it was in the seventeenth century that Parliament became indispensable to the Crown, not the during the sixteenth.