If you had got your hands on newly launched Nexus 5 Android smartphone then here is a good news for that now you can root it and install custom apps on your Nexus 5. Once you had rooted your device you will be able to install custom ROMS on it which will come up very shortly.
Pre Requisites :-
Back up all your data, contacts and SMSs before you proceed
Enable USB debugging by heading to Settings > Applications > Development > USB debugging