Open your template.css at:
<Joomla Root>/templates/<your template name>/css/template.css

At the end of the lines, add below codes:

#roksearch_results .container-wrapper {font-family: "Arial";font-size: 12px;}
#roksearch_results .container-wrapper h3 {color: #f00;}
#roksearch_results .container-wrapper span {color: #000;}
#roksearch_results .roksearch_header {font-family: "Arial"}
#roksearch_results .viewall {font-family: "Arial"}