I'm pretty sure you're wrong.
This is Roberto Mancini's record vs Roma when he was at Inter:
04/05 - Roma - Inter 3 - 3
04/05 - Inter - Roma 2 - 0
04/05 - Roma - Inter 0 - 2 (Coppa Final)
04/05 - Inter - Roma 1 - 0 (Coppa Final)
05/06 - Inter - Roma 2 - 3
05/06 - Roma - Inter 1 - 1
05/06 - Roma - Inter 1 - 1 (Coppa Final)
05/06 - Inter - Roma 3 - 1 (Coppa Final)
06/07 - Roma - Inter 0 - 1
06/07 - Inter - Roma 1 - 3
06/07 - Roma - Inter 6 - 2 (Coppa Final) - Never Forget
06/07 - Inter - Roma 2 - 1 (Coppa Final)
06/07 - Inter - Roma 4 - 3 aet (Super Coppa)
07/08 - Roma - Inter 1 - 4
07/08 - Inter - Roma 1 - 1
07/08 - Inter - Roma 0 - 1 (Super Coppa)
07/08 - Roma - Inter 2 - 1 (Coppa Final)
8 Wins - 4 Draws - 5 Losses
How about before Mancini?
The losses vs Roma in one decade prior to Mancini arrival:
03/04 - Roma - Inter 4 - 1
01/02 - Roma - Inter 3 - 2
95/96 - Roma - Inter 1 - 0
94/95 - Roma - Inter 3 - 1
94/95 - Inter - Roma 0 - 1