Why did he bother answering his flipping phone then? Why did he bother coming out to see the job? He'd be working on the roof, it's not exactly crowded up there.
I had similar here.
Guy was supposed to come and clean our roof of moss, clean gutters and repaint the chimney stack.
He didn't turn up so I phoned him and said I was doing it myself (I'm now halfway-ish through) and he was really upset - said I was depriving him of business.
Like your roofer - he wouldn't have been anywhere near us and could've got on with the job. We've a detached property with decent gardens in a small village so it's not like he would be at risk.
In a similar vein I have a (what loosely could be called a friend) builder that I use occasionally. Father & son duo and live at the same address. They were supposed to be coming to do some work on the garden walls a couple of weeks back but he phoned and said (almost gleefully) that they were taking a Government paid holiday and would fit us in when they returned to work. I've cancelled that too and a guy in the village is, as I type, doing it instead. He's not been within 10 metres of us two all day.
I also have a friend who is a somewhat upscale builder (high-end properties and conversions) and he is really trying to keep the wheels on the bus so to speak. Subbies are his problem - they don't want to work right now despite the fact that on the several projects that he is working on at the moment it is very easy to keep to the distancing guidelines. All materials are available and he can plan for one sub' to work on each property for as many days as required in total isolation. He has told me that he wont forget and when they want work in the future, as they often do, they will get short shrift.