Medieval Christians said the rosary as Catholics still do today: by praying five decades of Ave Marias (Hail Marys), each introduced by a Pater Noster (Our Father), while meditating on three series of five mysteries each.
The rosary is a tool used to meditate on fasting.
The rosary is not a tool used for any aspect of fasting.
( z1 rosary :domain ( z2 tool :ARG1-of ( z3 use :ARG2 ( z4 meditate :ARG1 ( z5 fasten ) ) ) ) )