A bit of housecleaning first...
Delete all the page numbers you've inserted thus far. In Word 2003 or earlier, click on File | Page Setup | Layout tab, and turn off "Different first page" and "Different odd and even". In Word 2007, click on the Page Layout tab, click on the little arrow at the bottom right corner of the Page Setup group on the Ribbon, click on the Layout tab, and turn off "Different first page" and "Different odd and even".
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Insert some section breaks so that you can have different page number styles on different pages...
Insert a next-page section break (press Alt+I, B, Alt+N) between pages 1 and 2 in lieu of a manual page break. Insert a next-page section break between pages 4 and 5 in lieu of a manual page break. Now your document has three sections (page 1, pages 2-4, and 5+).
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Add page numbers...
Click somewhere in section 2. In Word 2003 or earlier click on View | Header and Footer, or in Word 2007 click on Insert | Header.
On the Header and Footer toolbar, turn off "same as previous" or "link to previous" (depending on what version of Word) in the section 2 header, arrow down to the section 2 footer and turn off... , arrow down to the section 3 header and turn off... , and arrow down to the section 3 footer and turn off... .
Arrow up to the section 2 header or footer, insert small roman page numbers starting at i.
Arrow down to the section 3 header or footer, and insert normal page numbers starting at 1.
And you're done!