What is the difference between 日本のロック and 日本語ロック?

I thought J-Rock (Japanese Rock) is supposed to be written in 日本のロック, but someone said it should be 日本語ロック. Are they both same or just different bit...?

My understanding is that, for example, 日本語本 means Japanese language book and 日本の本 is something like book about Japan?

Kaku-san said:

I thought J-Rock (Japanese Rock) is supposed to be written in 日本のロック, but someone said it should be 日本語ロック. Are they both same or just different bit...?
My understanding is that, for example, 日本語本 means Japanese language book and 日本の本 is something like book about Japan?

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日本のロック could mean Rock music performed by the Japanese artist(s), rock music in general in Japan, etc. and not necessarily songs in Japanese language.
日本語（の）ロック means whoever play it, it is in Japanese language.
日本語の本 means either books in Japanese language or books on Japanese language.
日本の本 means either books published in Japan, books about Japan, books available in Japan, etc.
日本 means Japan, 日本語 means Japanese language.

Look at it this way
アメリカンの音楽
I don't think you would say:
英語音楽
When speaking of Genre

If you want to speak of contents of music then maybe you would use. 日本語 or 英語。