In the last 25 years, the Rome final has had at least one of the RG finalists 9 times. I think it's been skewed because of Steffi's and Justine's absences. Otherwise it's not that bad.
1987 Steffi Graf Gabriela Sabatini 7–5, 4–6, 6–0
1988 Gabriela Sabatini Helen Kelesi 6–1, 6–7(4–7), 6–1
1989 Gabriela Sabatini Arantxa Sánchez Vicario 6–2, 5–7, 6–4
1990 Monica Seles Martina Navrátilová 6–1, 6–1
1991 Gabriela Sabatini Monica Seles 6–3, 6–2
1992 Gabriela Sabatini Monica Seles 7–5, 6–4
1993 Conchita Martínez Gabriela Sabatini 7–5, 6–1
1994 Conchita Martínez Martina Navrátilová 7–6(7–5), 6–4
1995 Conchita Martínez Arantxa Sánchez Vicario 6–3, 6–1
1996 Conchita Martínez Martina Hingis 6–2, 6–3
1997 Mary Pierce Conchita Martínez 6–4, 6–0
1998 Martina Hingis Venus Williams 6–3, 2–6, 6–3
1999 Venus Williams Mary Pierce 6–4, 6–2
2000 Monica Seles Amélie Mauresmo 6–2, 7–6(7–4)
2001 Jelena Dokić Amélie Mauresmo 7–6(7–3), 6–1
2002 Serena Williams Justine Henin 7–6(8–6), 6–4
2003 Kim Clijsters Amélie Mauresmo 3–6, 7–6(7–3), 6–0
2004 Amélie Mauresmo Jennifer Capriati 3–6, 6–3, 7–6(8–6)
2005 Amélie Mauresmo Patty Schnyder 2–6, 6–3, 6–4
2006 Martina Hingis Dinara Safina 6–2, 7–5
2007 Jelena Janković Svetlana Kuznetsova 7–5, 6–1
2008 Jelena Janković Alizé Cornet 6–2, 6–2
2009 Dinara Safina Svetlana Kuznetsova 6–3, 6–2
2010 María José Martínez Sánchez Jelena Janković 7–6(7–5), 7–5
2011 Maria Sharapova Samantha Stosur 6–2, 6–4
2012 Maria Sharapova Li Na 4–6, 6–4, 7–6(7–5)
I think because of its position as the final big leadup, Rome winners have tended to face a lot of pressure and crumbled at RG.