So here's what I did! First I created the main layout of my room using the shapes tool. Once I got all the desks in place, I locked the desks down. That's important because you just want to drag names around, and not the desks. (You can unlock them if you want to change your layout though).
To lock, just select all the items, right click, and you will see the locking option.
Then create a text box that says "Student Name". Copy and Paste this enough times to fill up your desks.
After that, duplicate the page for however many classes you have. I teach four classes. Click on the pages tab (it's on the upper right side). Right click on the page and click "Clone Page."
You can rename the pages to the names of your class too. Just right click on that page, click "Rename", and change the titles. Mine are Block 1A, Block 3A, Block 1B, and Block 3B as I teach on an A-Day/B-Day schedule.
Then, when you get your class rosters at the beginning of the year, just type in the "Student Name" text boxes to replace them. Do this for all your classes and then you're done for the year! Just open up the file and make changes by dragging the names around. You can always add or delete names as well as students come and go. You can stand at your Smart Board and do it if you want to see the big picture. Sometimes I even let the kids do it :) And it's easy to print for your records and substitutes as well! Just select "Full Page" printing and it will print one page per sheet.