Rich Internet Applications (RIAs) Engineering is an emerging area of Software Engineering which lacks of development approaches and tools for support. The demand for RIAs is driven by the increase in the development of cloud-based applications. In the aim of helping to meet the growing need for support of RIAs engineering, an extension to the Phases Process for RIAs Development (PPRD) for source code generation of multi-device RIAs is proposed in this paper. As a salient contribution, our proposal covers multi-device applications in comparison with other approaches where they are focused on software modeling allowing the code generation in a semi-automatically way. In order to validate our proposal, we have generated a set of cloud services APIs-based multi-device RIAs.