well i have found this great online dictionary from Japanese to English and back. Maybe it is a good idea to submit it to the Links site of BtN?
Well, Rokusuke: roku means 'good, satisfactory, worthy' and suke means 'assistance', so in total rokusuke means 'good assistance'.
Hachidai: hachi means 'crown, pot' and dai means 'cost, price' (used only as a suffix). that would be 'price of a crown' or alike. well, this one was harder, because there are several meanings of hachi , like 'bee' and 'eight'.
About that 'eight': that is a funny coincidence, because roku also means 'six' and Hachidai and Rokusuke have written the famous song Sukiyaki together and those names are their real names.
About that online dictionary: this site is great. You can even find what English names and surnames would be in Japanese, like Hutchinson is Hacchinson and the French city Roquefort is in Japanese Rokkufooru . Many other possibilities.