In the Mangala Sutta, the Buddha says that one of the highest blessing is to support one's parents. Was this just meant for the lay people? Because elsewhere, he praises solitude and being alone in the forest to achieve salvation for oneself and others. If as a lay person due to job and other factors we are not able to be present physically to support one's parents, does this go against what Buddha required of us for our parents?
No it's not just for lay people. The Buddha himself has praised monks for looking after their parents. It's even allowed in the Vinaya.
As a busy lay person, you don't have to be physically present always. You can support them financially if they need it. If they don't need it, you can still send them gifts and visit them once in a while. That will not interfere with your meditation. It's about being grateful for what they have done for you. If you are ungrateful, you will not progress in the path no matter how solitary your life is.
In the time of the Buddha, people generally lived in clans & villages; basically in the same house; doing the same work. Therefore, supporting parents was simple; as was leaving the clan to become a monk (since there were many other relatives to look after the family). In today's modern world, these matters are more complex although often it can be easy (when we are not required to support our parents due to government pensions).