The answer is analogues structures evolved from two different ancestors.
A convergent evolution is a phenomenon of independent evolution of similar traits in species that are in different lineages. These traits are called analogues structures. They are similar in form or function but were not present in the last common ancestor of those species. So, the appendages of cockroaches and turtles are analogues structures with the similar function - creeping movements, and they are the result of the convergent evolution, but they evolved from two different ancestors.