The speed should be independent of the RIP you are using with one exception. Speed will be dependent on several factors including Head Speed. We recommend that every one of our customers install VersaWorks, even if they don't think they will use it. Eventually, users may find that they have to use VersaWorks when a profile is not available for Flexi or the RIP they are using. So, I'd recommend that all the updates are done (Firmware and Versaworks) and do a test print at Standard (360 x 720). This mode will realize a 100% increase in speed from 75 to 150 sfh with the update. Check to see what the Head Speed is when VersaWorks prints this image and set your 3rd party RIP to the same speed to realize the new throughput promised by Roland.
Also, check out the MANY new profiles available for VersaWorks. There are now tons of 3rd party media profiles, which are linked from Roland DGA to the Roland Japan site. This may make VersaWorks more desirable to users who need profiles for non-Roland products. I have found that other RIPs tend to lay down more ink than is necessary, while VersaWorks' profiles have good Ink Limits in their "canned" profiles.