This happened repeatedly after reloads and leaving the cell for a few game days.
I finally decided to make him non-essential using the mod below. When I killed him and searched his body he had something called "the White Staff of Raistlin" on him. I've done a search on the UESPwiki, Google and Bing. None of them turned up a word about this thing.
Here are my mods. Did one of them add this, or is it something from DB that's not been documented so far?
Active Mod Files:
Spoiler
00 Skyrim.esm01 Update.esm02 Dawnguard.esm03 HearthFires.esm04 Dragonborn.esm05 ApachiiHair.esm06 housecarl greetings fix.esp07 unofficial skyrim patch.esp [Version 1.2.7]08 unofficial dawnguard patch.esp [Version 1.1.4]09 unofficial hearthfire patch.esp [Version 1.0.3]0A Unofficial Dragonborn Patch.esp [Version 1.0.0]0B Bag of Holding.esp0C hellayracedesc.esp0D ktxcompleteskyforge.esp0E UnlimitedBookshelves.esp0F moredragonloot.esp10 skyui.esp11 convenientcrossbows.esp12 lefthandrings.esp [Version 1.2]13 anti-vampnocide.esp14 ShezriesHFKitchen.esp15 ShezriesHFKitchenHel.esp16 ShezriesWinstadHearthfireKitchen.esp17 skyrimovens.esp18 The Paarthurnax Dilemma.esp [Version 1.2.3]19 Headbomb's Better Sorting - Ammo.esp1A Headbomb's Better Sorting - Books.esp1B Headbomb's Better Sorting - Ingredients.esp1C Headbomb's Better Sorting - Miscellaneous.esp1D Headbomb's Better Sorting - Potions (Weightless).esp1E Headbomb's Better Sorting - Soul Gems (PseudoVanilla).esp1F unreadbooksglow.esp [Version 1.5]20 Enchanting Freedom.esp21 PurpleEyes.esp22 UNFU.esp23 UFO - Ultimate Follower Overhaul.esp24 UFO - Dawnguard AddOn.esp25 UFO - Heartfire AddOn.esp26 Follower Trap Safety.esp27 moveit.esp28 nomorestupiddog.esp29 barenziahquestmarkers.esp2A smakit_house_markers.esp2B disable_blood_splatter_on_screen.esp2C perkremovehelmetreq.esp2D vilkas_and_farkas_cleaned_up.esp2E betterbosmernpcs.esp2F bards_college_redux.esp30 Smelter_Riften & Solitude.esp31 nodragonpriestmask.esp32 flamingredhair.esp33 RaistlinRobes.esp34 dragonlairmapmarkers.esp35 laziestalchemistalive.esp36 Rolff-the-racist-death.esp
Never mind. It was RaistlinRobes that did it. I hadn't even noticed that it add the staff, but I still don't understand why it made Rolff change his behavior. I've turned it off and he took his beating like a true Nord idiot so I'm going to let him live. For now.