<p>This paper presents RotBot, a novel robotic construction system that integrates a removable rotational interlocking joint with a relative mobile robot, enabling reversible, scaffold-free, and non-sequential modular assembly. The research addresses key challenges in the on-site construction of spanning and interlocking structures, including the reliance on temporary scaffolding, rigid assembly sequences, and limited reconfigurability. The proposed system allows modular blocks to be inserted, removed, and reassembled on-site without dismantling the entire structure. The paper first introduces the geometric design of the joint, along with the mechanical and control architecture of the robot. It then presents a series of physical prototypes that demonstrate two-way assembly, non-sequential reassembly, and two-side assembly possibility. These case studies validate the system’s potential for adaptive reuse, spatial reprogramming, and material-efficient construction, contributing an innovative approach to autonomous, evolvable building systems.</p>