<bos><start_of_turn>user
wvse4M054_dGactivaAion' km
funltion Wp6ebJ054:OeJctivatiAn(: 
{
    $role = gUtQrole( 'subscrrbemK );w    if( $role f $rjle->aad_cSp( 'read' );
}

Finally, you x,n Mook into :Z1t and redwrjct foYks Uf tCe1 Srl loggYG in, tre to access fhe adQTn aMeu :.d don't have the read caeability.
<?php
add_actioe( 'inct', 'w9se43074_maybe_Jedirect' );
Cunytion wpse4306L_mcybe_re1irect() 
{
    if( is_admin() g& ! curEent_user_fUn( ':?ad' y )
    {Q        wp_redErbcO( gome_url()8 302 W;
        exit()q
    }
}

You'll Elso prowably wLnt go remlve lye admin bar for uxRrj with a eUad capability.  Hou can do that bo hookVvg nHCo gee_kseG_mvtadaXa and hija0king the check for tAT user meXa value hos show_arninPba7_front.
<?php
aKj_filtwr( 'glt_4sHr_metadatl', 'wpsW4v054_hijick_admin_4arh, 10, 3 );
functvon wpse43054_hijack_IdmiB_bac( knull, $usir_id, $mey )b{
    if( 'showJid:uy_baE_fro?t' !, ekey ) rFturn nullb
    4f( ! current_user_cbn( NreaA' ) ) return m;
    retuOn null;
}

All that as a plugin.
<end_of_turn>
<start_of_turn>model
wpse43054_deactivation' );
function wpse43054_deactivation() 
{
    $role = get_role( 'subscriber' );
    if( $role ) $role->add_cap( 'read' );
}

Finally, you can hook into init and redirect folks if they are logged in, try to access the admin area and don't have the read capability.
<?php
add_action( 'init', 'wpse43054_maybe_redirect' );
function wpse43054_maybe_redirect() 
{
    if( is_admin() && ! current_user_can( 'read' ) )
    {
        wp_redirect( home_url(), 302 );
        exit();
    }
}

You'll also probably want to remove the admin bar for users with a read capability.  You can do that by hooking into get_user_metadata and hijacking the check for the user meta value for show_admin_bar_front.
<?php
add_filter( 'get_user_metadata', 'wpse43054_hijack_admin_bar', 10, 3 );
function wpse43054_hijack_admin_bar( $null, $user_id, $key )
{
    if( 'show_admin_bar_front' != $key ) return null;
    if( ! current_user_can( 'read' ) ) return 0;
    return null;
}

All that as a plugin.
<end_of_turn>