A timer solutiuon may require a smart hub like Wemo or Smart Things which has more advanced scripting.
Otherwise an Alexa Routine can be made like "Lights Out" and you can assign all lights you want to it and set them to off.
Because I have SmartThings, I can make Scenes, so I have one called Red Alert and another called Lights Out. When a security event happens, the Red Alert scene is called, turning on all my lights. I've also made a Alexa Routines of the same names, and when I say "Good Night", it activates the Lights Out scene.
So I have several ways of getting the lights out, but since I say Good Night, every night, I know Alexa will get all the lights and whatever else I want done at bed time.
Alexa can recognize Scenes, but I don't recall if it can make them. For me, it's something I import from SmartThings when I sync, so I manage it there, and then wire up additional Alexa behaviors in the Alexa app.