roasted way more pimento peppers than I need. Can I freeze them or otherwise preserve them? For how long?
You can store them in a little olive oil in a covered container in the refrigerator for two, maybe three weeks; the taste and texture will be fine.
For longer storage, lightly film a cookie sheet with an oiled paper towel. Place a single layer of peppers on the sheet and freeze them. When they're solid, put them in a plastic bag and store in the freezer for up to three months.
A friend once brought me a bag of fire-roasted mild chiles from New Mexico--they still had the skins on. She told me to freeze them and I did and they were fine. The skins just fell right off when I defrosted them and they were good, even for chiles rellenos.