Inflate the tubes as hard as you would normally for everyday use, as you mention you need to have the pressure behind the roller which allows the correct profile of the strake to bond to all areas of the fabric. Preferable to use a heavy roller, usually brass, if not then any decent DIY shop should have a wooden or plastic one.
A tip for the sanding, get a dremel with a small pink 'v' shaped sanding stone, be careful and start at a low rev range. The glue will flick off easily and detailed areas are easy, masking tape is essential before grinding and applying glue.
Hopefully you also have some thinners, degrease before glueing and to remove any excess! 12 hours or so before use.