Beardie and a Snake

So I just moved and in my new apartment I am keeping my snakes and my bearded dragon in the same room. They have been in the same room for about a little over a week, and there have been no problems. My Hognose is extremely energetic and playful and loves digging around and trying to climb the sides of his tank. He has done this multiple times every day, and my beardie didn't seem to mind them. Suddenly today, my Hoggie was climbing around as usual, and my bearded dragon got extremely upset. His beard got very black, and there has been a lot of head bobbing. Why does he suddenly care, and should I keep them in seperate rooms? (The only other room I have is my bedroom, where I have a female bearded dragon that my male gets very aggressive about as well. I am worried she might not be too happy about my Hoggie either)

So long as they are in separate enclosures and not seeing each other all the time , I think they'll be fine.

In the wild bearded dragons view small snakes as food items, larger snakes than them are seen as predators and something to be feared , we have a lot a large pythons and venomous snakes here in Australia who share the same natural range as central bearded dragons , many species of which take even full grown adult bearded dragons if the can catch them or bite them.