。
O sun, my friend, keep shining on me.
Literal
Friend-being sun [vocative-よ] me [object-を] illuminate-continue [request-てくれ].
Deeply literary: 友なる uses the classical attributive copula なり (→ なる) to say 'sun which is my friend.' よ is the vocative particle, addressing the sun directly. 俺 is the rough masculine first-person pronoun. 照らし続けてくれ chains three elements: 照らす ('illuminate') + 続ける ('continue') + てくれ ('do it for me'). A poetic invocation.