For those that don't know about it, one of the MB members puts in a huge effort to maintain an up to date cap work sheet for the Texans. Here is a Link
to aj's cap work sheet.
As far as the rookie pool, some of the information on the FA signings is still not publicly available (see note at bottom of aj's work sheet) so the Texans seem to have about $7.5 mil in cap space. Plenty to work in the rookie pool.