Make the first three pages a separate section and set its numbering to Roman numerals. Make the second section restart numbering at one.
Here's how:
1. At the top of the first page you want Arabic-numbered, click the Page Layout->Page Setup->Breaks icon.
2. Insert a Next Page type section break.
3. Click the Insert->Page Numbers->Format Page Numbers menu item.
4. In the Page Numbers dialog box, click the Format button.
5. Since you don’t want the page numbers to be continuous between the two sections, set Page Numbering to start at number one. The radio button should switch to Start At.
6. Click OK.
7. Go back to the first page of the document (now in the first section).
8. Repeat steps 3-4, but this time set the Number format to Roman Numerals.
9. Repeat steps 5-6. (Note: The actual insertion of page numbers in the page header or footer doesn't have to happen. Only the formatting selection is necessary. To avoid the insertion, click the Cancel button instead of the OK in Step 6))