By use of infinitive in the first sentence, the adverb "imposingly" does not refer to 'love' but to how she talks.
The second sentence has two clauses.
1) She loved speaking romantically. Here speaking is the object of the verb love and the adverb modifies love. As: She romantically loved speaking
2) when there was an occasion. Is a relative adverbial clause modifying adverb ‘romantically’.
In the third sentence the infinitive to hear is the object of verb love and linked with an adverbial clause Roberta talk about them.