Roy announced the date for vote of confidence after meeting Meghalaya Governor R.S. Mooshahary.
Earlier in the day, Health and Family Welfare Minister, Advisor Pariong, belonging to coalition ally Hill State Peoples Democratic Party (HSPDP), resigned from the government.
The ruling coalition was reduced to 30 members on Wednesday after Urban Affairs Minister, Paul Lyngdoh, belonging to the Khun Hynniewtrep National Awakening Movement (KHNAM) withdrew support.
Pariong's 'disappearance' was preceded on March 9 by the withdrawal of support to the MPA by two independents, Limison Sangma and Ismail R. Marak.
However, the chief minister claimed that Pariong resigned only from the Cabinet and not from the MPA.
Pariong, who sent his resignation to the chief minister by a messenger, was reported missing since Wednesday night by his party.