Learn Spanish (Latin America): Eran los padres a quienes les rogamos que valoraran la disciplina. - They were the parents we begged to value discipline.

The verb rogar (to beg) is a verb of influence. Because the begging happened in the past (rogamos), it forces the action we wanted them to do into the past subjunctive. We begged that they value (que valoraran) discipline.

Is rogamos in the present or the past tense in this sentence?

It is in the past (preterite) tense here. For -ar verbs, the nosotros form is spelled exactly the same in both the present and the preterite (rogamos can mean 'we beg' or 'we begged'). We know it is the past tense in this sentence because the surrounding verbs (Eran, valoraran) are in the past.

Why do we need both a quienes and les? Isn't that redundant?

Yes, but Spanish requires this redundancy! Both refer to the parents ('to whom'). Whenever an indirect object phrase like a quienes comes right before its verb, you must also include the matching indirect object pronoun, which is les.

Why use a quienes instead of just que?