Nuts are not entirely toxic for pigs. There are some beneficial aspects to them as well. For example, these contain fiber which is helpful for your guinea pig’s excretory system. Moreover, nuts can also fulfill their dietary requirements for micronutrients like magnesium, potassium, copper, selenium, and phosphorus.  Though roasting nuts can lower fat content by a few percent, these are still unhealthy for your pet. You should not include nuts, whether plain or roasted, in your guinea pig’s diet. Their minor health benefits couldn’t outcome the significant clinical risks.