www.re.rockspace.local is an local website that will only open if you are connected to your rockspace wifi device. If you are already gone through the setup process then you do not have to access this website. In case you need to change your wireless password or some other settings you may have to find the ip address of your rockspace extender.
If you are not able to access www.re.rockspace.local then you might have to check your connection between the extender and the device you are using it on. Usually people get this issue when the connection between their device and the extender is not yet made.
However in order to access www.re.rockspace.local you can simply connect your device with rockspace wifi and open your browser to check if you are able to access this website. If you are still facing issues with it you may have to try resetting your extender first but before you even start resetting your device you should check the light status on your rockspace range extender.
Sometimes users face this issue because they already have their device connected to the router. Check the light status on your extender to ensure if your extender is already connected to the router. If your extender has 2 solid blue lights that means your extender is already connected. If not then reset your extender once and set it up again.