Adding 2 cents to the wise suggestions above, I drink diluted tonic water through the day (hoping that quinine helps, but lots of water intake anyway). I also try to stretch at every possible moment. That is gently but firmly moving limbs as far as they want to go, then with steady pressure wait for them to elongate to their full extent. A favourite is putting each heel in turn up on a sofa back while standing on the other leg (as if hurdling), it helps to be able to lean on something for balance. Then wait as my knobbly knee descends till the leg is straight, then just to test myself try to pull toes towards me. Another is to stand on a doorstep (or similar) with one foot, the edge across the ball of the foot. Then try to relax the calf muscle to allow the heel to drop as low as possible. I find it relaxes even further if I pull the foot up against resistance (the down heel) then swap feet. I do these two while I brush and floss my teeth to make sure that I'm as stretched as possible before sleep.
I find that what helps is not just rolling and stretching out of muscles, but this done in conjunction with pulling in the opposite direction. As if by pulling the antagonistic muscle, it helps the paired muscle to relax better. So pulling the toes up, acts to help the muscles that pull toes down (calf) relax more. As if we're coaxing muscles to calm down, take it easy, ... get out of their fussing and tensing.
I find that trying to stretch in bed tends to lead to cramps. But if I massage and bend legs by hand, that seems to help. Nighttime loo trips can be a bit stampy, as if I've a bolt through my neck; but they are a stretch opportunity too.
Rachel, I've no idea how different your cramping/stiffness may be from mine. But I find that experimenting has helped. For me it helps to not think of stretching and relaxing as a torture but rather as an indulgence, a pleasure to look forward to. Rather than feel that tight muscles are some hostile force attacking me, rather that muscles (nerves) are favourite animals that need stroking and coaxing to keep them happy.
Sorry to ramble. I do empathise with what you're going through Rachel.