converse.js/sass/_roomslist.scss

#conversejs {
    .list-container {
        text-align: left;
        padding: 0.3em 0;

        .rooms-toggle {
            font-family: $heading-font; 
            display: block;
            color: $text-color;
            padding: 0 0 0.5rem 0;
            &:hover {
                color: $dark-gray-color;
            }
        }
        .items-list {
            text-align: left;

            .list-item {
                border: none;
                clear: both;
                color: $text-color;
                display: block;
                height: 2em;
                overflow: hidden;
                padding-top: 0.5em;
                text-shadow: 0 1px 0 $text-shadow-color;
                word-wrap: break-word;
            }

            .available-chatroom,
            .open-headline,
            .open-chatroom {
                &:hover {
                    background-color: lighten($controlbox-head-color, 45%);
                }
                &.unread-msgs {
                    .msgs-indicator {
                        border-radius: 10%;
                        opacity: 1;
                    }
                    .available-room,
                    .open-room {
                        width: 100%;
                        font-weight: bold;
                    }
                }
                a {
                    &:hover {
                        color: $dark-link-color;
                    }
                    &.room-info {
                        &:before {
                            font-size: 15px;
                        }
                    }
                    &.open-room {
                        width: 68%;
                        float: left;
                        overflow: hidden;
                        text-overflow: ellipsis;
                        white-space: nowrap;
                        padding-right: 0.5em;
                    }
                    &.available-room {
                        width: 85%;
                    }
                }
                .add-bookmark,
                .remove-bookmark {
                    &.button-on {
                        color: $link-color;
                        &:hover {
                            color: $dark-link-color;
                        }
                    }
                    color: $subdued-color;
                }
            }
        }
    }
}

#conversejs.fullscreen {
    #controlbox {
        #chatrooms {
            .bookmarks-list {
                dl.rooms-list.bookmarks {
                    dd.available-chatroom {
                        a {
                            &.open-room {
                                width: 80%;
                            }
                        }
                    }
                }
            }
        }
    }
}