If you've replaced your system WebKit it should be fine.
I generally Relink instead, when you download Leopard WebKit inside the DMG there is a relink app, simply drag Roccat onto it, it will then create a Roccat LWK.app that app will be then be relinked so when you open it.
Best to make sure you have latest Leopard WebKit as the latest version fixes various Roccat issues.