A major upgrade over the basic RK-9000, the RK-9100 now also has a two port USB 2.0 hub installed. USB 2.0 ports found on keyboards are usually low power and those on the RK-9100 are no exception; the keyboard had no problem powering on mouse receivers, a Wi-Fi adapter and USB flash drives but an external 2.5" mechanical HDD would not always start.
The back of the RK-9100 is seemingly uninteresting, being almost entirely plain, with the exception of the anti-skid rubber strips on the four corners of the keyboard and the height adjustment legs. The legs also have rubberized edges, meaning that they will still not be any more slippery than the rubber strips found on the base of the keyboard if you decide on using them.
Rosewill is proud of the braided cable which they used on the RK-9100 and are heavily advertising it. It may be "just a cable" but it does enhance the quality of the keyboard, both in terms of aesthetics and durability. The connectors are gold plated, which Rosewill claims that they will reduce latency. We are unsure whether that will help in any measurable amount but it is a fact that gold plated connectors improve the quality of electrical connectors. The downside is that you will have to use both USB connectors in order for the lighting to work.
Once powered, the LED lighting of the Rosewill RK-9100 creates a very strong visual effect; so strong that you will be thankful that Rosewill added brightness settings, as it is almost impossible to work in a very dark room with the keyboard set at maximum brightness and full illumination. There are three settings; the first is the normal mode which illuminates the entire keyboard, the second is the gaming mode where only the WASD and arrow keys are illuminated and the Windows keys are disabled, and the third is a peculiar mode where only the numpad is turned off. There are only two quirks with the keyboard's lighting: First, the keyboard will always default at mode 1 and maximum brightness every time the system is powered on. Second, the brightness of the green LEDs on the lock keys is not adjustable, which can be a problem because the light is quite strong, even if only the Numlock key is turned on.