well, you would need to follow several steps:
0) make backup of important data !!!!
1) make a directory into your / partition called /home2 (for example).
2) copy the contents from /home to /home2. To do that you have two options:
a) cp -a /home/* /home2/
b) cd /home2 && tar cvf home.tar /home/* && tar xvf home.tar && rm home.tar
3) comment the /etc/fstab line with the /home entry (putting a # at the beginning of the line).
4) umount /home and rename /home to /home_bak (for example).
5) rename /home2 to /home
6) reboot and check that all is ok.
6) Empty your old /home partition and merge with / partition.
....That would be all..... more or less