Page numbering and format can be defined per section so you can get to the required format by creating two sections in your document and setting the page numbering accordingly
Start with an empty document
"Insert - Auto Page Number", select the "Section" option for "Show In" and set the format to roman numbers. This is now your TOC section.
Use "Insert - Section break" to create a new section
"Insert - Auto Page Number" again, select the "Section" option for "Show In" and set the format to arabic numbers
With the cursor in the second section, open the inspector
and reset the the page number to 1