You can automatically send out upcoming weekly volunteer opportunities to your volunteers.  This email will contain a list of events/roles which they can sign up.  By default this configuration is turned off, but you can enable it and choose the day of the week you want to send out the email.

To enable, go to your admin dashboard and click Action and Configuration.  From there change the filter to Event.  Update the value for Notify Volunteer Openings to the day you desire, or 'Never' to disable this feature.

It's a good idea to review all the configurations as there are some really useful features.  Like sending admins a monthly birthday list!