What is the typical consistency of a roux?
Roux is very forgiving, and can be made a variety of consistencies, or ratios of butter to flour.  It should only be brown if you are intentionally making a brown roux, for the flavor.  Otherwise, it should be fairly yellow, closer to the color of the butter.

At the canonical ratio of 1:1 butter to flour (by volume), the consistency will be thick enough not to flow, but certainly not as thick as wet sand.  (When refrigerator cold, if you store it, it will be quite firm and thick, scoopable with a spoon with some effort.)

You can heat the butter at any speed you like consistent with not burning it.  You can heat it at fairly high heat until the foaming begins to subside, which indicates that the water has been boiled out.

I generally recommend adding the flour after the butter is melted, and stopped bubbling (which indicates the water is gone.)