Hi Bhavik
You can not consume the RFC Directly.
Because SAP UI5 is a open source and is not a integrated and tight framework as in WD Java or WD Abap where you can directly consume using JCO's in case wdjava and a just RFC call in WD Abap.
Here in SAPUI5 as a open framework only understands the open protocols like json,xml or oData.
So at any cost your RFC has to be converted /exposed to the one of these protocol
That is what the Netweaver Gateway comes into the picture.
Use Gateway to publish RFC as a oData Channel URL so that you can consume easily
Hope this will help you.
Regards
KALYAN