The Cardinals 2002 rookie pool was :
Arizona Cardinals 8 picks $3.750 million
Last year we had an extra 3rd round pick. So, I would expect 2003's rookie pool to be about the same.
Only picks in rounds 1 - 4 really count towards the cap. Picks 5-7, if they make the team will push a player that makes more money off the team, so those players actually save some cap space.
So, set aside about $3M for rookies. The Cards also like to save about $1M to pickup players during the season to replace players put on IR. Note, almost all other teams don't do this. Most teams ride right up to the cap and if players need to be added during the season, they either cut someone or rework a contract.