Nothing in Catholicism prevents protestants from praying the Holy Rosary, any novenas, to the Saints, to Mary, or any prayers.
Any obstacles thereto, would come from their respective/specific Protestant belief.
Confession is a little trickier.
In a nutshell:
Non-Christians and those who share the Christian faith but who have not been baptized cannot receive confession since baptism is the door to the rest of the sacraments. In fact, the function of confession is to restore the grace which was originally conferred on a person in baptism but which has sense been lost through (mortal or venial) sin. The early Church Fathers thus called confession “the second plank after the shipwreck,” the shipwreck being the sin in which we are born, baptism being the first plank which we may grab hold, and confession being the second plank we may grab hold if we let go of the grace of the first.* Thus only baptized people can go to confession.** If a person isn’t baptized, his first job is to get that sacrament.*
jimmyakin.com/can-protestants-go-to-confession
I say trickier, because the protestant denominations vary so much in so many aspects, that basically some administer baptism which the Church recognizes a valid, while some don’t (e.g.–‘dedication’ =/= Baptism). However, Baptism is incredibly basic–any Church so much as splashes water on one, and does so in the name of the Holy Trinity–their baptism would be recognized as valid.
There’s actually even more to it than that–see the article posted in the link above, by Jimmy Akin.
fwiw.
