You need to install rpmbuild (yum install rpm-build) modules to used the command below. This is just my note regarding command I need to used.
Directory under /usr/src/redhat
BUILD RPMS SOURCES SPECS SRPMS
cd /usr/src/redhat/SPECS
rpmbuild -ba nameofyourspec.spec
This will produce rpm and rpms files, That will reside under directory /usr/src/redhat/RPMS and /usr/src/redhat/SRPMS
Another command I love to used is to identify the file came from what package.Directory under /usr/src/redhat
BUILD RPMS SOURCES SPECS SRPMS
cd /usr/src/redhat/SPECS
rpmbuild -ba nameofyourspec.spec
This will produce rpm and rpms files, That will reside under directory /usr/src/redhat/RPMS and /usr/src/redhat/SRPMS
rpm -qf /usr/src/redhat
rpm-build-4.4.2-48.el5