Earlier today I found out that our beloved auther, John Ronald Ruel Tolkien translated the Hail Mary, Our Father and Glory be into elvish. So, yes, you can say the Rosary in elvish.
Hail Mary:
Aia María quanta Eruanno
i Héru aselyë
aistana elyë imíca nísi
ar aistana i yávë mónalyo Yésus
Airë María Eruo ontaril
á hyamë rámen úcarindor
sí ar lúmessë ya firuvammë: násië
Glory Be:
alcar i Ataren ar i Yondon ar i Airefean
tambë engë i et...
Our Father:
Átaremma i ëa han Eä
na airë esselya
aranielya na tuluva
na carë indómelya
cemendë tambe Erumandë
ámen anta síra ilaurëa massamma
ar ámen apsenë úcaremmar
sív’ emmë apsenet tien i úcarir emmen
álamë tulya úsahtienna
mal ámë etelehta ulcullo: násië