Set branch based on AD company Value

I don't understand why you need to assign value to session.custom.company.role!!!

if you need it, the expression is:

session.custom.company.role = 
if { ( [mcget {session.ad.last.attr.company}] equals "Company A" ) || ( [mcget {session.ad.last.attr.company}] equals "Company B" )} {
    return "value of the role"
} else {
    return "other value of the role"
}

or of you want to assign a different role for every company:

session.custom.company.role = 
if { ( [mcget {session.ad.last.attr.company}] equals "Company A" )} {
    return roleA
} elseif { ( [mcget {session.ad.last.attr.company}] equals "Company B" )} {
    return roleB
} else {
    return "other value of the role"
}