Online Rubric is a Google Spreadsheets Add-on that enables to you create rubrics, enter scores, and email scores to students all from one place. Online Rubric provides very clear instructions for each step of the processes of creating a roster sheet, creating a rubric, and emailing grades to students.
To start using the Online Rubric Add-on open the Add-ons menu in a blank Google Spreadsheet. Select "get Add-ons" and search for Online Rubric.