Second that meaning. "God is my rock" simply means this person turns to God as their sanctuary or stronghold or foundation. Someone who bears this name is someone who depends or leans on God.
The meaning is clear to me. Rock means strength or stability. A loose translation would be "God is my strength." Rock is just a broader symbol than just strength alone. I really like the name.
Unless you're a pantheist, or a devoted fan of rock music, the meaning doesn't make any sense. ("My rock is God"? Uhh, congratulations!) Nice name anyway, though. Love the spelling, love the sound.