From the Rhone valley, the Col de la Croix is a BIG challenge with more than 1300m of climbing. The upper part meanders through woods and pastures all the way to the top at 1775m.
The road from Ollon to Villars is busy and too narrow to accommodate cars and cyclists. You should avoid it and climb from Bex. There are few cars and the views are great. Both roads join in Villars and the final section to the pass is beautiful.