This is dependent on the roof bars you have and the amount useable roof bar space, as well as the width of the box and the bike racks. If you go for the right roof bars it's usually possible to fit two bike carriers alongside a choice of roof boxes.
Aluminium through bars will always provide you with the most useable amount of roof bar space, so it’s always best to choose these over the aluminium flush bars or steel square bars, especially if you are needing as much space as possible. Flush bars are not usually long enough to carry a roof box and a bike.
You'll also need to take into account the maximum load or your car roof and/or roof bars (be guided by the lower amount if they differ).
You'll often have to use T-track fittings for both the bike carriers and roof box. These fittings slide into the channel on the top of aluminium bars, meaning you can use the full length of the bar to attach your gear. If you use 'around-the-bar' fittings they may clash with the roof bar feet. T-track fittings are supplied with some roof boxes and bike carriers and are available separately in a lot of cases.