even if you have roadshow installed, you should try this installer and the option [s] and tune the settings, as roadshow default ones are set for really old days. I've gone from ~1MB/s wgetting a ubuntu iso with default roadshow settings, then after tweaking with my installer, same file is downloaded with ~4MB/s
maybe the tweak settings should be as a seperate tool..as the importance of setting these settings maybe gets lost since its mainly an installer...