If a recipe calls for instant coffee, can just regular ground coffee be substituted? When instant coffee is called for in a baking recipe, can regular ground roasted coffee be used? Will the same amount work?
Unlikely that you will run into any problems, although chemically they won't behave the same way. Instant coffee completely dissolves while the ground coffee will be in there as solid pieces that soak up some water and add taste. I assume the total amount of coffee used is just too little to affect the composition of the dough very much.

You could however also substitute some of the liquid in the recipe with brewed coffee. I think that's the way I would go with. That way you just have the desired taste without changing the composition and ratios of the recipe.