A pot of dry rice is considered a solid food, whereas soup is of course, a liquid. However, not all foods can be classified so easily. Rabeinu Yerucham states that there is considerable debate as to what the opinion is because there are variant texts. Some say that any liquid whatsoever in the food renders it a liquid and is forbidden to place on the blech once it has cooled. Accordingly, the only type of cold food permitted to put on the blech would be a dish that was absolutely dry. Even food with only a small amount of gravy would not be allowed to be put on the blech. Other Rabanim hold that we look at the majority. A food is only designated a liquid if it is comprised mostly of liquid.
Ha’Rav Ovadyah Yosef (a”h) subscribes to the opinion that we consider the majority. However, he explains that this does not mean we measure the volume of solids and liquids in the pot. A soup that has a significant amount of vegetables is still considered a liquid even if technically, there are more vegetables than soup. A soup is a soup. We look at the nature of the item: is it essentially a dry food or a liquid food? A roast by nature is a dry food. Even though the roast contains moisture which is sometimes secreted, that moisture is secondary to the food.
In such a case where the liquid comes from the item itself and is a small amount, Rav Ovadyah is lenient. Anything more than that, where the liquid is separate from the item itself, if it is basting or soaking in it, then even Rav Ovadyah is machmir and forbids returning it to the blech once it has cooled. One is permitted to empty out the gravy and then place the dry food on the blech.