Heat oven to 400°F. Cut the top from the garlic head to expose the cloves, drizzle with roasting oil and wrap in foil. Roast for 35 to 45 minutes until soft, then cool for 10 minutes.
Meanwhile, bring egg-cooking water to a gentle boil in a saucepan. Lower in eggs and simmer for 11 minutes, then transfer to the ice and cold-water bath for 10 minutes.
Peel eggs and grate them on the large holes of a box grater. Squeeze roasted garlic from its skins and mash into a smooth paste.
Mix garlic paste, yogurt, dressing oil, lemon juice, dill, salt and pepper. Fold in grated eggs, cover and refrigerate for 30 minutes until thoroughly cold; chilling is included in preparation.
Place one dry lettuce leaf on each croissant bottom and divide egg salad over the leaves. Add drained roasted pepper strips in a separate layer.
Close the sandwiches and serve cold or refrigerate at 40°F or below until serving.