The NextGen gallery plugin is compatible with WPtouch and WPtouch Pro. There are a couple of things that may be contributing to the issue you're seeing. First, ensure that your gallery images are not using fixed dimensions. Fixed dimensions, by definition, override any scaling functions of your OS and of WPtouch. You'll want to stick with flexible dimensions or not specify them at all and simply upload images at the dimensions you desire.
You may also want to check that other plugins are conflicting with your WPtouch/WordPress configuration. To isolate which plugin(s) may be contributing to the trouble, deactivate all except WPtouch from within the WordPress Plugins area, clear your browser cache and local data, then test.
If WPtouch functions well, you may then enable the rest of your plugins one at a time, repeating the process, until you can identify which is/are causing the problem.