They combined Radioman and IT into one role so you end up managing quite a lot of systems. I slept in the radio shack more often than I slept in my bed while at sea. My crew was 12 people IT/Radio for a 300 person ship. There are so many different responsibilities within this role, satellite communication systems especially, that usually 6/12 people would be glued to one area of the radio shack for hours and hours working or waiting on one system but the radio shack was at least half full at all times.
We had varying hourly schedules for coverage throughout my 4 years aboard including: 12 on, 12 off - 8 on, 8 off - 6 on, 6 off. In addition to your normal job you must also perform hardware maintenance on your own time and you have a tertiary job related to combat/warfare (mine was firefighter) so you end up doing constant drills/training on top of your actual work. Everyone on my ship lived on Monsters and Pre-workouts.
While on shore every 6 days you have what is called "Duty". Duty is a 24 hour work window where I did my job for 10 hours and then did one or two 4-hour roving shifts. Roving is essentially just surveying the ship with armor and an m-16. Me and a colleague hated these roving shifts so we would purposefully set systems to alarm at opportune times to get us off those roving shifts so we could do our 4-hour duty shifts in the radioshack, where we work on personal projects or just watch anime off an external hdd.
A Submarine's crew is about half the size of my ship so I'd guess they have around 5-6 radioman/IT but I could be wrong.