Not sure why a separate risk assessment would be required...
Not even sure I know what you mean... Are you referring to a risk assessment of NOT complying (probably not recommended), or a residual risk assessment of trace hazardous substances that may still be present even though RoHS directive has been met?
I think probably line items in whatever risk assessment you have dealing with materials is probably sufficient:
- Hazard: poisoning by hazardous substances in materials, environmental contamination
- Risk: (evaluated)
- Mitigation: RoHS compliance SOP, materials testing..etc.
- Verification: Materials data, test-reports etc.