Like a lot of Android users I suffer from the Roon app closing and having to reconnect when it’s in the background or phone goes to sleep or screen off.
Today I noticed in Settings, Setup Keep Screen on. I turned this on and it’s now staying active all the time when in the background and does not seem to loose connection.
Obviously you need to remember to put it in background or lock your screen or it will keep your screen on but it’s a small sacrifice to make it stay active. Give it a go and see if it helps.