Red bell peppers freeze really well after being roasted. This is the method I would recommend for you.
The problem with freezing first is that it can degrade the peppers (breaks the firm cell walls) and would likely make them more difficult to roast afterwards. If you roast them first, the cooking starts the cell collapse itself and the peppers don't tend to degrade more afterwards, plus your peppers are already roasted, so you've saved yourself that step in your pasta making process.
The process is pretty simple... roast as usual, parcel into recipe-sized portions in small zip top bags (don't forget to date the bags) and freeze or roast, put on a cookie sheet (if you have one that fits in the freezer), and freeze in a single layer. Once frozen, they can all go in one big bag and they shouldn't stick to each other too badly.
Here's a guide that explains the process with some roasting tips. And another here.