I do that with Simple Commands by kloee. Set it to arm at 12:15 if I forget to do it at bedtime. You just write a routine in Simple Commands then include it in an Alexa routine. Or, alternatively, the SC routine can run autonomously on a timer. Also, SC can detect the alarming state of Ring and perform other tasks such as turning on lights, auxiliary sirens, etc.
Easy to use and free! SC greatly increases the utility and convenience of Alexa and Ring and lets you use (some) 3rd party products that may not otherwise be compatible (I use Tula plugs and lamps).