You copied the Doc URL to your clipboard.

What is a root region?

A root region is a region with the same load and execution address. The initial entry point of the image must be in a root region. If the initial entry point is not in a root region, the link fails and the linker gives an error message.

LR_1 0x040000          ; load region starts at 0x40000   
{                      ; start of execution region descriptions	      
    ER_RO 0x040000     ; load address = execution address
        * (+RO)        ; all RO sections (must include section with 
                       ; initial entry point)
    ...                ; rest of scatter-loading description