Hi, My 6 month old is now in his own room. I breastfeed him when he wakes during the night. I go in 15 mins after he is asleep to check that he’s not too hot/cold and follow safe sleep guidelines I’m just wondering how often I should check him during the night? Should I be setting alarms to go in and check on him?

Red Nose recommends Room Sharing for the first 6 months.
You are not expected to get up regularly to check on baby after they have moved to their own room, particularly at this age, but if you do wake, then also use the time to check on baby.

Parents are not expected to observe their baby constantly. If your baby is sleeping in a separate room check baby regularly to ensure that the baby remains on the back and the head and face remain uncovered (as baby grows beyond 5-6 months they will move around the cot and roll over; settle baby to sleep on their back but let them find the sleep position they feel most comfortable in. A safe cot and safe sleep environment is still necessary for babies older than 5-6 months).
https://rednose.org.au/article/room-sharing-with-baby

Is your baby rolling yet & preferring to sleep on tummy or side?