Yes, it is okay to give them your direct number but I always find it best to still use your Rover numbers. When this becomes very helpful is if there is ever a dispute between you and the client, Rovers trust and safety team is able to see your exact communication with the owner.
As long as you and the owner have your phone numbers registered through Rover (which normally we do, it is set up when we first started the system.) You are able to text the client as normal, using their Rover number (and vice versa). It will pull up as a regular text message to their phones. You can send pictures and communicate just the same.
(Just to try clarifying a little better) when you text them from your cell phone, the number that appears on their phone is your Rover number. even though you used your regular cell phone. And when they text you back using your Rover number it will automatically go to your regular cell phone text messages)
And even though you are texting the client through your cell phone, as long as you are using the rover number that was provided for the client , all of your communications through texting will also appear on the rover site. This also includes pictures.
So to answer your question yes you can but you can do the same with using thier rover number and it works just the same except it still goes through the Rover platform.
(sorry if it sounds confusing, it really isn't, but best way I know how to explain it.)