1937 Christian Brothers arrive in Roscommon and the Monastery and Secondary School are built from monies of Conmee Bequest. From the earliest times the school is known as C.B.S. Roscommon. Br Maloney is first Superior
1939 Primary School built from same fund
1942 Br Kennedy Superior
1948 School Bus purchased to bring students from surrounding areas to school. This was the first such service probably in the country. It was organised by Br Creed new Superior in Roscommon.
1948 Connacht Senior Football A Champions
1949 Past Pupils Union formed
1952 Br Murphy Superior
1955 Br Mullins Superior
1958 Br Horgan Superior
1964 Br Lawlor Superior
1967 New prefabricated classrooms and Science room added to cater for increased numbers following introduction that year of Free Second Level Education.
1970 Br Heffernan Superior. He established Parents Council.
1974 New extension built to the front of the Secondary school to accommodate continuing growth in student numbers as full impact of Free Second Level Education is absorbed and much higher numbers enrolled and a greater percentage of students go on to Leaving certificate.
1976 Br O’Sullivan Principal
1979 Br Donnelly Principal
1982 Br Hannon Principal
1987 Christian Brothers withdraw from Primary Education in Roscommon and a new Parish School for boys was built known as Abbey National School. The Primary school building is incorporated into the Secondary school following some renovations.
1988 Br S. Crowe Principal
1994 A new extension is opened which replaced the Prefabricated building, (not in use since 1987) adding a second assembly area a new Science Room and an Administration area.
1995 First appointment of lay Principal for C.B.S. Secondary School. Mr P.J. Carrig
1996 Beatification of Blessed Edmund Ignatius Rice in Rome on 6 October
1998 Connacht Senior Football A Champions
2002 Bicentenary of the opening of first school by Br Rice in Waterford
2003 Second lay Principal Mr M. Fahey
2005/06 New equipment for Science Rooms and Computer Room and new classroom furniture.
2006 Christian Brothers withdraw from direct involvement in teaching and leave Roscommon town in August.
2007 Third lay Principal Mr Pat O’Hanlon, from Kilkenny
2008 New prayer room opened.
2010 Mr O’Hanlon leaves in November Mrs J Connaughton becomes Acting Principal
2011 All Ireland Colleges B Football Champions
2011 Ms J Connaughton becomes first female principal