For floor construction....the thicker the better. and the fewer the seams the better. I use at least 1/2 or heavier ply wood. Use construction adhesive (glue the plywood to the joists) if you can and long decking screws to keep the wood in place. Then I simply cover with a piece of carpet.....as long as the blind is sealed well it's not an issue. If it's not then you just replace the carpet scrap with a new piece every year or so. The thing with a rolling chair is you need the carpet to stay put....otherwise it wants to roll and bunch up and it's just frustrating. You can fix that with using some "tacking strips" at the edges and screwing them down (washer can help as well).....you just unscrew to replace the carpet later if needed. For some reason I have better luck with torx head screws vs regular "+" type heads as well.