[unix] How to use variables in a command in sed?

I have abc.sh:

exec $ROOT/Subsystem/xyz.sh

On a Unix box, if I print echo $HOME then I get /HOME/COM/FILE.

I want to replace $ROOT with $HOME using sed.

Expected Output:

exec /HOME/COM/FILE/Subsystem/xyz.sh

I tried, but I'm not getting the expected output:

sed  's/$ROOT/"${HOME}"/g' abc.sh > abc.sh.1

Addition:

If I have abc.sh

exec $ROOT/Subsystem/xyz.sh $ROOT/ystem/xyz1.sh

then with

sed "s|\$INSTALLROOT/|${INSTALLROOT}|" abc.sh

it is only replacing first $ROOT, i.e., output is coming as

exec /HOME/COM/FILE/Subsystem/xyz.sh $ROOT/ystem/xyz1.sh

This may also can help

input="inputtext"
output="outputtext"
sed "s/$input/${output}/" inputfile > outputfile

This might work for you:

sed 's|$ROOT|'"${HOME}"'|g' abc.sh > abc.sh.1