The complexity of today's robot control systems implies difficulty in developing them efficiently and reliably. Systems engineering (SE) and frameworks come to help. The framework metamodels are needed to support the standardisation and correctness of the created application models. Although the use of frameworks is widespread nowadays, for the most popular of them, Robot Operating System (ROS) version 1, a contemporary metamodel, has been missing so far. This article proposes a new metamodel for ROS (MeROS), which addresses both the running system and developer workspace. For compatibility with the latest versions of ROS 1, the metamodel includes the latest ROS 1 concepts such as nodelet, action, and metapackage. An essential addition to the original ROS concepts is the grouping concepts, which provide an opportunity to illustrate the decomposition of the system, as well as varying degrees of detail in its presentation. The metamodel is derived from the requirements and then verified on the practical example of the Rico assistive robot. The matter is described in the SysML language, supported by standard development tools to conduct projects in the spirit of SE.