Not silly no, and my answer is; I wouldn't use roots. Reason being that they are the parts that take up the water for the plant but also retain some responsibility in holding glucose and other 'toxins'.
The best wood to use is that which has come from a branch or a limb, this way it will dry out leaving its 'skeleton' which is the part that is aquarium friendly. The layer under the bark called the cambium is the layer through which the food is transported, and once this has dried it is fine to use. This layer is alot thicker in evergreens and also retains alot more 'sap' after death.
The wood to stay away from is greenwood, which is the 'live' wood of the tree. The live wood had the 'sap' inside its cambium and will leak in small amounts.
Roots do not have a bark layer and use the entire structure of roots in the transportation process, which means they are full of toxins or 'sap'.
Other plants to stay away from are bamboos and grasses. Bamboo does not conform the same structure as a shrub or tree. Bamboo, being a grass, uses all of the stem in its transportation process.