Obviously I don't want to have to recreate these pages each time I publish my paper, so I would like to know if there is a way to create reusable master pages/templates.
First, you didn't say what version of Scribus you are using or what platform you are using it on. If you are not using 1.4.0 Release Candidate 6, I urge you to move to it. And in the future, it's a good idea to mention version and platform when asking questions in a forum like this because the answers are sometimes different.
Having said that, there are couple things to consider.
1) You can create a plain document with text styles and master pages, and then just import the ones you want into any Scribus document. This document can contain all styles and master pages for any document you might want to create, not just the newsletter.
2) Scribus does support templates, and comes with a few, but you will no doubt want to create your own. A template is basically just a document that you use over and over, saving it under a new name for each subsequent issue so as to maintain the template document unchanged.
A long time ago I had a newsletter that I published every two months. Most of the layout was the same, just the stories and some of the artwork changed for each issue. After I had created the first issue I deleted all the transitory stuff and saved it under a new name as a template. The template contained the masthead, text styles, margin settings, and lots of other things that I wanted to maintain with each issue so as to give a uniform appearance. Each time I created a new issue I opened the template, saved a copy with the a name reflecting the date of the issue, then closed the template.
Note that you don't actually have to create a Scribus template to accomplish this. You could just use a plain document and use "template" or something in the name so you won't accidentally overwrite it with changes.
It will take you a bit of planning and thought to create your template, but it won't take much time and it will save you hours for each new issue.