Very sweet babies
So very sorry about their mama
they are fortunate to have you
Here are some links to raising orphaned rats
http://www.rmca.org/Articles/orphans.htm
http://www.afrma.org/orphanrm.htm
I have been told the best formula to give is squirrel replacer for orphaned squirrels, next best is KMR (kitten milk replacer from a vet) and then organic soy infant formula for human babies.
Once their eyes are open, in addition to hand feeding each baby many times per day (see the above links), you might also put down a shallow dish of formula thickened with a bit of baby cereal (the kind that says add milk) and when they are ready they will start to try it .... but will still need to be hand fed. Baby rats are gradually weaned as they try foods and domestic rats wean themselves by 5 weeks of age. If the babies you have were domestic then they would be around 13 or 14 days old.
A good facebook site is Deer Mouse Domesticated & Friends - people on there have raised orphaned wild baby rats and mice
You will need to handle the babies a great deal .... the more they get used to people when so young the better they will be able to adjust to captivity and the more likely they will be happy.
Here is a link that shows the normal development of domesticated rats. Wild babies develop slower.
http://ratguide.com/breeding/baby_development/birth_to_weaning.php
Here is a thread by a member who raised a wild orphaned baby
http://www.ratshackforum.com/forum/showthread.php?t=23622&highlight=Rhydian
and some info and experience on here
http://www.ratshackforum.com/forum/showthread.php?t=33354&highlight=Rhydian
Please ask continue to ask questions, post pics, and provide updates
all the best to you and the babies