What will they do in winter when there's a foot of snow on the ground?
Low roofs/short coops have a number of issues.
Good ventilation should be well above their heads.
Such a low metal roof may have condensation issues in winter too.
Frostbite may more of an issue than with a higher roof...
2' high is not conducive to putting roosts higher(which they might appreciate and use) or for ventilation in winter.
Pics of coop, inside and out, might help garner viable suggestions/solutions.