It is possible to fit a ski carrier next to a roof box, assuming your roof bars are long enough. Ski carriers do take up more space on the bars that some people imagine, so you may well be limited to quite a narrow roof box.
You can find both the loading width and the total width of a particular ski carrier on the 'specifications' tab. You'll need to make sure your bars are long enough to fit both the ski carrier and roof box.
Just get in touch with us if you would like us to check a particular combination.
You'll also need to be mindful of the maximum loading weight of your roof bars and car roof.