Roppongi clubs can be be somewhat touristy &/or meat market, with very few exceptions. The advantage is that these places don't charge standard Japanese cover charge which runs up from 1500 yen to 3500 yen or so.
Harlem and Vuenos are good suggestions for recent commercial style hip hop and both places sometimes do reggae nights. Reggae nights are generally pretty rare (maybe only a 2 or 3 big ones in a month). You'll want to check http://iflyer.tv/en-jp/
and do a search for hip hop or reggae in "Kanto" on the night you are looking to go out.
"Family" and "Nuts" (both Shibuya) are smaller and a bit more underground and also worth checking. Micro clubs like "grass roots" (Koenji) might also be worth probing.
There are also a large number of reggae bars that do events on fridays or saturdays. These won't be listed on iflyer so some intensive googling would be the best way to find locations and schedules. "Drum Song" in Shimokitazawa is the only one I know personally. This place is generally pretty "Rootsy" but they sometimes do ska or dancehall or even caribbean roots events as well. http://blog.livedoor.jp/drumsong757/
The site is a bit hard to make sense of so drop me a message if you are interesting in going there and I'll send you a google map link or something.
Thanks a lot!
All precious informations!!
If you have a smartphone, download an app called "Clubberia." You can search Tokyo nightlife by location in the city, venue, or music genre. They also have coupons for cover and junk like that!
Two of the oldest and best reggae clubs in Tokyo are Club Jamaica (dancehall reggae) in Nishi Azabu and Open (Roots Reggae) in Shinjuku Gyoenmae. Neither Harlem or Vuenos does much reggae (though Harlem is mainly hip hop). Harlem used to have a policy that single FOREIGN males (i.e. foreign males not accompanied by a female) were not allowed in. This did not apply to Japanese. I kid you not. I'm not sure if this is still the case but Harlem is best avoided if only to protest this racist policy.
There is a roots reggae bar on the main drag in Roppongi (just before the two Turkish restaurants side-by-side) and a number of other ones dotted around the city.
Drop me a line if you'd like further info