It's hard for me to recommend stuff cos the line between j-pop and j-rock is kinda blurry to me too. I think by some definitions hitomi , for example , could fall under 'j-rock' too.
I'm kinda embarrased to admit I like Shunsuke Kiyokiba's debut album. He's one of the few male j-artists I listen to , and I think his music falls under j-rock.
here's few songs off that album:
Sayonara Iitoshii hito yo
Utai Hito