The former Manchester United man, who signed for the Foxes in the summer, has played a pivotal role in the Development Squad this campaign, scoring a brace in the 6-2 win over Manchester City in late October that sparked a run of four consecutive victories.
The 20-year-old previously tasted Championship football in the 2013/14 campaign, when he played 19 times for Yeovil Town while on loan from Manchester United, scoring twice in the process.
A player boasting pace, skill and an eye for goal, Lawrence will certainly benefit from his time with the Millers, who currently sit 22nd in the second tier of English football.
Lawrence will look to steer his new side away from the relegation zone when they host bottom club Blackpool on Saturday before they travel to Cardiff the following weekend.