Welcome

What email service and what client (Windows Live Mail etc)

OK Windows mail is your client, but you need a provider. Bring up Windows mail. On the top you will see acounts, click on that. On the left you will see your provider.
It will be the name of your ISP (the company that give your your internet, or Yahoo Mail, or Gmail, etc)

We may have enough information to begin making educated guesses. With RoadRunner, go the the website for a while to get your mail. See if it is maked as spam at the website. If it is, Roadrunner has a procedure that while the mail is being read, click on not spam.

If it does not work, post and we will talk again tomorrow.

If the spam notice is coming from Roadrunner, there is something that sets off the spam notice, words in the text, the source of the email (the email provider, in your case RoadRunner). Your last post indicating that it does not always happen, shows that there is some common element in all the questioned mail. If you look at them carefully you may be able to detect the cause. If you get email on a regular basis that is being marked, put that address in your address book and that will stop it.
If you stop a few because of the source, once you accept that source several times, the problem should stop. We have to wait and see.