Deadlifting heavy gets a bad reputation because some people get injured. But the most common injuries come from bad form and/or the spine alternating positions throughout the lift.
Rounded thoracic RDLs will allow you to introduce spinal flexion under small loads. And they'll help you gain the strength you need in your spinal erectors to protect the mid back and up.
An important factor is allowing your scapula to protract and retract to its full extent as well as creating as much spinal flexion and extension as possible.