You don't need the kernel sources to check if your current kernel supports raid.
What sort of raid support do you mean? Software raid or support for a particular raid card? The softraid modules are called md-mod raid0, raid1, raid5,... just try modprobing them. For raid controller support you'd need to know the module name that supports the particular card you need. Many distros place the kernel config in /boot under the name of config.<kernel version> You can look through there to see if support is compiled in should the modprobe fail. Or else you might find the kernel config under /proc/config.gz