Don't use ROM Manager!!!!
It'll brick your phone!!!!
Don't even think of installing ROM Manager on your phone. All it's gonna do is brick your phone....
So my advice is, abstain from using ROM Manager until they officially support our phone.
Till then, use the unofficial port of Clockwork Recovery Mod by tj_style.
the complete package is also attached with this post.
DO NOT FLASH IT ON FROYO!!!
If you need any further assistance, please continue the discussion here.
Download CWM.ZIP here
It seems like adityam533 has found a method to make ROM manager work on G-Fit.
For further details, go >>>here<<<