Yes, if the roof is metal and reflecting, you can try and take advantage of that property
Though, if it's reflecting it in a bad way (i.e. it's a ridged roof or something causing severe multipath), it may actually be better to block the reflections from the roof with a metal screen (think faraday cage)
Though, if it's reflecting it in a bad way (i.e. it's a ridged roof or something causing severe multipath), it may actually be better to block the reflections from the roof with a metal screen (think faraday cage)