If you have an existing Novel AI subscription, you can use it in conjunction with AI Roguelite.

PLEASE NOTE: All NovelAI models (including Erato) are currently outperformed by Free Cloud and Paid Cloud for most situations, even including NSFW scenarios. This option makes sense for users who already have a NovelAI account and want to try out different writing styles. If you're just looking for a premium text generation service, consider Paid Cloud instead.

Go to novelai.net and ensure you're logged in
Click the gear icon to get to User Settings
Go to "Account" and click "Get Persistent API Token"
Copy/paste the token into AI Roguelite's NovelAI Key field.