Here is one way of doing it,
assuming that user is stored in local storage (or you can save it in the state of redux),
var user = localStorage.getItem('user')
if (user) {
user = JSON.parse(user)
}
inside return()
:
<Switch>
{/*any user*/}
<Route exact path='/' component={Home}/>
<Route exact path='/home' component={Home}/>
<Route exact path='/about' component={About}/>
<Route exact path='/contact' component={Contact}/>
<Route exact path='/register' component={Register}/>
{/*admin*/}
{user && user.role === "ADMIN" &&
<>
<Route path='...' component={...}/>
<Route path='...' component={...}/>
<Route path='...' component={...}/>
</>
{/*user*/}
{user && user.role === "USER" &&
<>
<Route path='...' component={...}/>
<Route path='...' component={...}/>
<Route path='...' component={...}/>
</>
<Route component={NotFoundPage}/>
</Switch>