I don't believe it's trilled. These sites list the differences between old and modern pronunciation, but don't mention R, leading me to believe that the pronunciation hasn't changed. http://wmich.edu/medieval/resources/IOE/pronunciation.html http://people.umass.edu/sharris/in/gram/GrammarBook/Pronunciation.html

The Old English R was trilled, much like the trilled R in modern Dutch. We almost never use it in modern English, except for a rare old upper-class accent.

擬音只是擬音, 是沒法完全正確的, 古代R到底是什麼音值只是個擬音, 你想怎麼發都可以, 又沒人可以穿越到過去聽聽古代英格蘭人究竟怎麼講話, 就跟中古漢語擬音一樣, 任何語言擬音都只能做參考, 沒哪個語言學家可以告訴你絕對正確的發音