If a birch sapling has a block above it, no amount of bonemeal will allow it to grow. This occurs even when the block is by far out of the 6 blocks above range described by the wiki; I tested leaving a gap of up to 20 air blocks between the block and the block and the sapling. 

The problem isn't a roof because, as shown in the pictures, the sapling grows fine with a roof 20 blocks above, as long as there is a hole directly above the sapling.

This is potentially a duplicate of MC-163403.