The Roman Cohort Fortress of Vindolanda was wood as late as 105 AD. The Fortress was converted to stone by 200 AD. Vindolanda was located near Hadrians Wall. Many Roman Fortresses followed this pattern; first a wood fort and if justified later conversion to stone.
I agree that marching camps of wood were temporary structures. Roman Forts were not designed to withstand siege; but to prevent a surprise attack and allow a Legion to form up march out and fight the enemy in the field. Legions lost in battle were in many cases ambushed on the march before they could deploy. Boudicca destroyed the IX Legion in this manor as it marched to relieve Camulodunum in 61 AD