Note - the sources listing for this database doesn't show a Cam & Kiltoom RC parish. A Kiltoom civil parish exists, but it wasn't created until 1864.
For Mic(hael) Mullen M 1850 +/- 4 yrs, Co. Roscommon, I found 3 rcds: 1846 Ballintubber/Ballymoe, 1849 Castlerea, and 1854 Athleague RC parishes.
For Mary Dillon M ditto, I found 3 rcds: 1849 Aughrim, 1849 Tibohine-Fairymount, and 1850 Tibohine-Fairymount RC parishes.
It appears that there are NO matching marriage rcds for these two. This infers: 1) the rcds didn't survive; 2) they haven't been transcribed; 3) they married elsewhere, or 4) some of your info is wrong. This bodes ill for the existance of their B rcds.
For H(annah) Cunningham M 1827 +/- 5 yrs, Co. Roscommon, I found 0 rcds. Without a rcd for Hannah, this means the rcd for Patrick doesn't exist in Co. Roscommon either.
For H(annah) Cunningham B ????, Co. Roscommon, the earliest rcd is for 1829 - too late for your timeline. Again, this infers the rcd didn't survive, hasn't been transcribed, or occurred in another county.
For Pat(rick) Mullen B 1803 +/- 4 yrs, Co. Roscommon, I found 0 rcds. Only two of Roscommon's RC parishes were keeping B rcds in 1803.