During his time in college, Roy was influenced by the radical nationalist movement during the First Partition of Bengal.

But as protested against the Rowlatt Act, he resigned in displeasure with the British Ruler and went to England to study law again in 1919 at Lincoln's Inn but did not complete the course.

After the 1946 Indian provincial elections, Roy led Congress negotiations with Huseyn Shaheed Suhrawardy to form a Muslim-League coalition government but negotiations broke down due to disputes over issues such as the release of political prisoners and distribution of ministerial offices between Congress and the Muslim League coalesced with opposition to a Congress-Muslim League coalition by the Congress and Muslim League high command.

Roy critiqued Suhrawardy for his complicity in the Direct Action Day communal riots in Calcutta.

[5][6] Like Sarat Chandra Bose, Roy was vehemently and persistently opposed to the partition of Bengal and was naturally a supporter of the Provincial Coalition Party and Forward Bloc Congress led by Sarat Bose.

Rajagopalachari's 1944 Rajaji formula which essentially conceded Pakistan on condition that it come about with plebiscites in Muslim-majority regions and the Partition of Punjab and Bengal.

Roy supported Frederick Burrows and Louis Mountbattens proposal for the representative coalition government and joint electorates in Bengal.

Whilst Muhammad Ali Jinnah initially provided tacit support to the United Bengal scheme, the All-India Muslim League high command would also oppose the scheme with the Nazimuddin faction, in contrast to the Suhrawardy faction, of the Bengal Provincial Muslim League supporting Partition and inclusion in a unitary Pakistan.

He was a prominent member of the Sabuj Patra Patrika edited by Pramatha Chaudhuri and the Monday Club by Sukumar Roy.