County Roscommon on Wikipedia.

Athleague, St. Patrick (R.C., 1842). M 830 575. © Gerard Close (2017). Link.

Ballaghaderreen, The Cathedral Church of the Annunciation of the Blessed Virgin Mary and St. Nathy, (R.C.). Two further views - 1, 2. All from old postcards in Reg Dosell's Collection. Link.
Boyle, St. Joseph (R.C.). G 8080 2677. From an old postcard in Reg Dosell's Collection. Joseph Cantwell has advised that this church was destroyed in a fire in 1977. The new church of St. Joseph was built on the same site. Its interior. Both © Joseph Cantwell (2012). Adoration Chapel was used as the parish church from the destruction of the old church, until the new one was built. Another view. Both © Joseph Cantwell (2012). The remains of Boyle Abbey (Cistercian). Four more views - 1, 2, 3, 4. G 8057 2725. All © Peter Morgan (2025). Link. The (former?) Presbyterian/Methodist Church on Carrick Road. The date-stone reads Presbyterian, and possibly 1858. G 8024 2501. © Peter Morgan (2025). Another Methodist Chap. shows on older maps (it pre-dates one of 1838) off Main Street at G 8022 2709. Its remains were seen by Streetview in 2024. Church of Ireland on Green Street, as seen by Streetview in 2011. G 8021 3053. Link. The 1838 maps also shows R.C. Chapel at the western edge of the town on Chapel Street, at G 7973 2576. By 1914 it had become St. Patrick's Hall. Since demolished, its site was seen by Streetview in 2024. Also shown on large scale maps, a little way S.W. of the town is Assylin Church (in Ruins), at G 7909 2098. Not visible to Streetview, it's not obvious from aerial views whether anything of it survives, though A.I. suggests it does.

Castlerea, St. Patrick (R.C., 1903). The tower was added in 1916. M 873 643. © Joseph Cantwell (2012). Interior view, and the East window, both © John Balaam (2016).
Cloonyquinn, St. Catherine (R.C.), which is also known as Killina Church. M 847 839. © Gerard Close (2017). Link.

Roscommon, Sacred Heart (R.C.). © Joseph Cantwell. Another view, © Gerard Close (2017).