Pet Pigeon???

Hi all, we have a new pet...Percy/Phillis the lost racing pigeon who was found last night by the annex door and it was too tired to move or fly away...sooooooooooooo after a lot of scratching our heads out came a cat carrier and in went Percy. We then googled 'what to feed a Pigeon' and 'what to do with a lost racing Pigeon' and we had a look in the cupboards for Pigeon friendly food so out came the rice and sunflower seeds!!! Percy then spent a night on the kitchen floor with seeds and water to munch on ;o) It was worrying as it was just sat there doing nothing...do pigeons do stuff??? But today it had eaten everything we put down for it and was bright and alert so we decided to clean the box out before Aidy went to work ... outside ... Pigeon is now on the roof and won't come down =o( so not sure what to do now. I have googled 'how to get pigeon off the roof' but not really into shooting it down!!!! And it says on lots of sites that the owner will just kill it as it failed to get home. Is this true??? So what do we do now???? Can't let it be killed, can't keep it on the roof...