What is "roolwer"

Roolwer was an eleventh-century ecclesiast. He is the first named bishop of a jurisdiction which later became the Diocese of the Isles, and appears to have served at his post before, and perhaps during, the reign of Gofraid Crobán, King of Dublin and the Isles. Roolwer's name appears to correspond to the Old Norse Hrólfr, which could mean that he is identical to either of two contemporary like-named bishops of Orkney. Roolwer's predecessor in the Isles may have been Dúnán, whose death in 1074 during the Dublin overlordship of Toirdelbach Ua Briain, King of Munster, may have enabled the ecclesiastical separation of Dublin from the Isles. The site of Roolwer's cathedral is unknown, although Maughold and St Patrick's Isle are possibilities.