Simultaneous recovery of lanthanum (La), cerium (Ce), and niobium (Nd) from sedimentary rare earth ores (SREO) has been carried out by a hydrometallurgical process using a sulfation roasting - leaching process (SRLP). Response surface methodology (RSM) was used to optimize the process parameters. The optimum condition for rare earth elements (REE) recovery was determined to be roasting temperature 700 °C, roasting liquid/solid ratio (L/S) 1.35 mL/g, roasting time 15 min, leaching temperature 90 °C, leaching L/S 20 mL/g, and leaching time 4.24 h. The maximum predicted recoveries for La, Ce, and Nd were 80.93 %, 74.48 %, and 97.49 %, respectively. The leaching verification experiments showed that the % leaching under the optimal conditions were La 88.02 %, Ce 78.87 %, and Nd 89.75 %, respectively. The % leaching relative deviation between the experimental and predicted values was less than 10 %, confirming the reliability of the experiments. Mechanism analysis shows that after SRLP, the florencite and kaolinite in SREO are more likely to be selectively converted to aqueous solution by H₂SO₄, thus achieving the separation of La, Ce, and Nd from SREO. This provides a valuable reference for the recovery of REE from florencite-base rare earth ore.