Hi. I'm not sure if this post is in the right section, so I apologize if it isn't. I was in my house and this guy called "Roadside Guard" came into my house and started attacking me. He was an essential character so I assume he has a quest. I can't talk to him because he keeps attacking. I have a bunch of bounty in the Pale (where my house is), i am a vampire, and I have Serana with me. Are those any of the reasons for him attacking me? I'd appreciate any information about how to make him not attack me anymore.

You have a Bounty. Turn Yourself into the Pale Gaurd near the Lorius Farm. You may be teleported to Dawnstar and have Your stolen goods removed, but it should end the Roadside Gaurd attacking Your character. You may need to run to Dawnstar if the "Roadside Gaurd" is the Pale Gaurd that patrols the Lorius Farm.

Thanks! Why is he invincible? Does he have a quest?

Yes, he is the replacement for the Pale guard that patrols neer the jester's carriage: http://www.uesp.net/wiki/Skyrim:Roadside_Guard

he is part of the Quest "Delayed Burial"

Follow the road north from Whiterun, you will eventually run into a Jester named Cicero by a broken down cart..

that is the quest Roadside Guard is part of

Aww... I can't do the quest because I joined the Dark Brotherhood. Oh well.