Arabica, you sound so calm in what must be such a stressful and uncertain situation.
My dd was in NICU/SCBU for 2 weeks after birth whilst a parade of doctors evaluated the extent of her heart condition and then for 1 week at 4 months when she had corrective surgery. I roomed in throughout. dd was my first, so I did not have other children to worry about.
When you say you are rooming in, is Esja with you in a room? Or do you just get a bed/chair next to Esja's cot in an open ward (I've seen that!). Is your room near the ward or in another section/floor? I found the best arrangement was to stay as close to dd as possible but with my own room/bed. But I appreciate you prob don't have much a choice, depending on your Esja's condition and availability of rooms.
I echo Pamina3 that you should try to get out at least once a day. Don't eat the hospital food (disgusting) - try to get your partner/visitors to bring in food if they can that you can just up in the microwave. I kept myself busy with frequent expressing, taking comfort that I was helping dd in some way, even whilst she was being tubefed.
Find out when the doctors do their rounds and hang around during that time to get the latest update on your dd's condition. If the hospital allows, get involved with her routine care, like changing her nappy, giving her baths, cuddles - I found it helped me to bond with dd, hard as it was.
Little personal touches, like a radio, books, magazines.
Take care of yourself. Esja is in good hands