Oct 21 (Reuters) - Canada’s commodity-heavy main stock index retreated from a record high on Thursday, weighed by weakness in miners and energy stocks, while dismal corporate earnings from Rogers Communications further dented sentiment. At 9:31 a.m. ET (13:31 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 60.11 points, or 0.28%, at 21,128.08. Reporting by Amal S in Bengaluru; Editing by Ramakrishnan M.