Some ingredients taste better than others when they're reheated after being frozen. Most lasagna recipes that call for fresh ingredients will be just fine after freezing, whether you freeze them unbaked or baked. However, if the recipe uses items that have already been frozen and thawed once, it's best not to freeze and thaw them twice. This increases the chance that the food could be contaminated by bacteria.
For example, don't plan on freezing lasagna made with sausage or ground beef that was previously frozen. Instead, use fresh meat or leave it out completely. Food that is frozen and thawed more than once also suffers when it comes to flavor and texture. Choosing a recipe that calls for fresh ingredients will result in the best-tasting lasagna. If your favorite lasagna recipe calls for a frozen ingredient, the final dish usually won't be too affected by substituting the fresh version instead. For example, instead of using frozen mushrooms, just use fresh. In most cases you will have needed to thaw them anyway.